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Chronological List of Mechanical Inventions and Technical Contrivances
A canal having been formed to connect Edinburgh with the Forth and Clyde Canal, and so to give a direct water-way communication between Edinburgh and Glasgow, I heard much talk about the desirableness of substituting Steam for Horse power as the means of moving the boats and barges along the canal. But, as the action of paddle wheels had been found destructive to the canal banks, no scheme of that nature could be entertained. Although a tyro in such matters, I made an attempt to solve the problem, and accordingly prepared drawings, with a description of my design, for employing Steam power as the tractive agency for trains of canal barges, in such a manner as to obviate all risk of injury to the banks.
The scheme consisted in laying a chain along the bottom of the canal, and of passing any part of its length between three grooved and notched pulleys or rollers, made to revolve with suitable velocity by means of a small steam-engine placed in a tugboat, to the stern of which a train of barges was attached.
The steam-engine could thus warp its way along the chain, taking it up between the rollers of the bow of the tug-boat, and dropping it into the water at the stern, so as to leave the chain at the service of the next following tug-boat with its attached train of barges. By this simple mode of employing the power of a steam-engine for canal boat traction, all risk of injury to the banks would be avoided, as the chain and not the water of the canal was the fulcrum or resistance which the steam-engine on the tug-boat operated upon in thus warping its way along the chain; and thus effectually, without slip or other waste of power, dragging along the train of barges attached to the stern of the steam-tug. I had arranged for two separate chains, so as to allow trains of barges to be conveyed along the canal in opposite directions, without interfering with each other.
I submitted a complete set of drawings, and a full description of my design in all its details, to the directors of the Canal Company; and I received a complimentary acknowledgment of them in writing. But such was the prejudice that existed, in consequence of the injury to the canal banks resulting from the use of paddle wheels, that it extended to the use of steam power in any form, as a substitute for ordinary horse traction; and although I had taken every care to point out the essential difference of my system (as above indicated) by which all such objections were obviated, my design was at length courteously declined, and the old system of horse traction continued.
In 1845, I had the pleasure to see this simple mode of moving vessels along a definite course in most successful action at the ferry across the Hamoaze at Devonport, in which my system of employing the power of a steam-engine on board the ferry boat, to warp its way along a submerged chain lying along the bottom of the channel from side to side of the ferry, was most ably carried out by my late excellent friend, James Rendell, Esq., C.E., and is still, I believe, in daily action, giving every satisfaction.
My kind friend and patron, Professor Leslie, being engaged in some investigations, in which it was essential to know the exact comparative total expansion in bulk of metals and other solid bodies, under the same number of degrees of heat, mentioned the subject in the course of conversation. The instrument at that time in use was defective in principle as well as in construction, and the results of its application were untrustworthy. As the Professor had done me the honour to request me to assist him in his experiments, I had the happiness to suggest an arrangement of apparatus, which I thought might obviate the sources of error; and, with his approval, I proceeded to put it in operation.
My contrivance consisted of an arrangement by means of which the metal bar or other solid substance, whose total expansion under a given number of degrees of heat had to be measured, was in a manner itself converted into a thermometer. Absolutely equal bulks of each solid were placed inside a metal tube or vessel, and surrounded with an exact equal quantity of water at one and the same normal temperature. A cap or cover, having a suitable length of thermometer tube attached to it, was then screwed down, and the water of the index tube was adjusted to the zero point of the scale attached to it, the whole being at say 50° of heat, as the normal temperature in each case. The apparatus was then heated up to say 200° by immersion in water at that temperature. The expansion of the enclosed bar of metal or other solid substance under experiment caused the water to rise above the zero, and it was accordingly so indicated on the scale attached to the cap tube. In this way we had a thermometer whose bulb was for the time being filled with the solid under investigation, — the water surrounding it simply acting as the means by which the expansion of each solid under trial was rendered visible, and its amount capable of being ascertained and recorded with the utmost exactness, as the expansion of the water was in every case the same, and also that of the instrument itself which was "a constant quantity."
In this way we obtained the correct relative amount of expansion in bulk of all the solid substances experimented upon. That each bar of metal or other solid substance was of absolutely equal bulk, was readily ascertained by finding that each, when weighed in water, lost the exact same weight. The figure of this simple instrument will be found in the text. My friend, Sir David Brewster, was so much pleased with the instrument that he published a drawing and description of it in the Edinburgh Philosophical Journal, of which he was then editor.
One of the earliest mechanical contrivances which I made was for preventing water, in a liquid form, from passing along with the steam from the boiler to the cylinder of the steam-engine. The first steam-engine I made was employed in grinding oil colours for my father's use in his paintings. When I set this engine to work for the first time I was annoyed by slight jerks which now and then disturbed the otherwise smooth and regular action of the machine. After careful examination I found that these jerks were caused by the small quantities of water that were occasionally carried along with the current of the steam, and deposited in the cylinder, where it accumulated above and below the piston, and thus produced the jerks.
In order to remove the cause of these irregularities, I placed a considerable portion of the length of the pipe which conveyed the steam from the boiler to the engine within the highly heated side flue of the boiler, so that any portion of water in the liquid form which might chance to pass along with the steam, might, ere it reached the cylinder, traverse this highly-heated steam pipe, and, in doing so, be converted into perfectly dry steam, and in that condition enter the cylinder. On carrying this simple arrangement into practice, I found the result to be in every way satisfactory. The active little, steam-engine thenceforward performed its work in the most smooth and regular manner.
So far as I am aware, this early effort of mine at mechanical contrivance was the first introduction of what has since been termed "super-heated steam" — a system now extensively employed, and yielding important results, especially in the case of marine steam-engines. Without such means of supplying dry steam to the engines, the latter are specially liable to "break-downs," resulting from water, in the liquid form, passing into the cylinders along with the steam.
In fixing portions of work in the turning-lathe one of the most important points to attend it is, that while they are held with sufficient firmness in order to be turned to the required form, they should be free from any strain which might in any way distort them. In strong and ponderous objects this can be easily accomplished by due care on the part of an intelligent workman. It is in operating by the lathe on delicate and flexible objects that the utmost care is requisite in the process of chucking, as they are easily strained out of shape by fastening them by screws and bolts, or suchlike ordinary means. This is especially the case with disc-like objects. As I had on several occasions to operate in the lathe with this class of work I contrived a method of chucking or holding them firm while receiving the required turning process, which has in all cases proved most handy and satisfactory.
This method consisted of tinning three, or, if need be, more parts of the work, and laying them down on a tinned face-plate or chuck, which had been heated so as just to cause the solder to flow. As soon as the solder is cooled and set, the chuck with its attached work may then be put in the lathe, and the work proceeded with until it be completed. By again heating the chuck, by laying upon it a piece of red-hot iron, the work, however delicate, can be simply lifted off, and will be found perfectly free from all distortion.
I have been the more particular in naming the use of three points of attachment to the chuck or face-plate, as that number is naturally free from any risk of distortion. I have on so many occasions found the great value of this simple yet most secure mode of fixing delicate work in the lathe, that I feel sure that any one able to appreciate its practical value will be highly pleased with the results of its employment.
The same means can, in many cases, be employed in fixing delicate work in the planing-machine. All that is requisite is to have a clean-planed wrought iron or brass fixing-plate, to which the work in hand can be attached at a few suitable parts with soft solder, as in the case of the turning lathe above described.
My father possessed a very excellent acromatic spy-glass of 2 inches diameter. The object-glass was made by the celebrated Ramsden. When I was about fifteen I used it to gaze at the moon, planets, and sun-spots. Although this instrument revealed to me the general characteristic details of these grand objects, my father gave me a wonderful account of what he had seen of the moon's surface by means of a powerful reflecting telescope of 12 inches diameter, made by Short — that justly celebrated pioneer of telescope-making. It had been erected in a temporary observatory on the Calton Hill, Edinburgh. These descriptions of my father's so fired me with the desire to obtain a sight of the glorious objects in the heavens through a more powerful instrument than the spyglass, that I determined to try and make a reflecting telescope which I hoped might in some degree satisfy my ardent desires.
I accordingly searched for the requisite practical instruction in the pages of the Encyclopedia Britannica, and in other books that professed to give the necessary technical information on the subject. I found, however, that the information given in books — at least in the books to which I had access — was meagre and unsatisfactory. Nevertheless I set to work with all earnestness, and began by compounding the requisite alloy for casting a speculum of 8 inches diameter. This alloy consisted of 32 parts of copper, 15 parts of grain tin, and 1 part of white arsenic. These ingredients, when melted together, yielded a compound metal which possessed a high degree of brilliancy. Having made a wooden pattern for my intended 8-inch diameter speculum, and moulded it in sand, I cast this my first reflecting telescope speculum according to the best book instructions. I allowed my casting to cool in the mould in the slowest possible manner; for such is the excessive brittleness of this alloy (though composed of two of the toughest of metals) that in any sudden change of temperature, or want of due delicacy in handling it, it is very apt to give way, and a fracture more or less serious is sure to result. Even glass, brittle though it be, is strong in comparison with speculum metal of the above proportions, though, as I have said, it yields the most brilliant composition.
Notwithstanding the observance of all due care in respect of the annealing of the casting by slow cooling, and the utmost care and delicate handling of it in the process of grinding the surface into the requisite curve and smoothness suitable to receive the final polish, — I was on more than one occasion inexpressibly mortified by the sudden disruption and breaking up of my speculum. Thus many hours of anxious care and labour proved of no avail. I had to begin again and proceed ‘da capo’. I observed, however, that the surplus alloy that was left in the crucible, after I had cast my speculum, when again melted and poured out into a metal ingot mould, yielded a cake that, brittle though it might be, was yet strong in comparison with that of the speculum cast in the sand mould; and that it was also, judging from the fragments chipped from it, possessed of even a higher degree of brilliancy.
The happy thought occurred to me of substituting an open metal mould for the closed sand one. I soon had the metal mould ready for casting. It consisted of a base plate of cast-iron, on the surface of which I placed a ring or hoop of iron turned to fully the diameter of the intended speculum, so as to anticipate the contraction of the alloy. The result of the very first trial of this simple metal mould was most satisfactory. It yielded me a very perfect casting; and it passed successively through the ordeal of the first rough grinding, and eventually through the processes of polishing, until in the end it exhibited a brilliancy that far exceeded that of the sand mould castings.
The only remaining difficulty that I had to surmount was the risk of defects in the surface of the speculum. These sometimes result from the first splash of the melted metal as it is poured into the ring mould. The globules sometimes get oxidised before they became incorporated with the main body of the inflowing molten alloy; and dingy spots in the otherwise brilliant alloy were thus produced. I soon mastered this, the only remaining source of defect, by a very simple arrangement. In place of pouring the melted alloy direct into the ring mould, I attached to the side of it what I termed a "pouring pocket;" which communicated with an opening at the lower edge of the ring, and by a self-acting arrangement by which the mould plate was slightly tilted up, the influx of the molten alloy advanced in one unbroken tide. As soon as the entire surface of the mould plate was covered by the alloy, its weight overcame that of my up-tilting counterpoise, and allowed the entire apparatus to resume its exact level. The resulting speculum was, by these simple arrangements, absolutely perfect in soundness. It was a perfect casting, in all respects worthy of the care and labour which I invested in its future grinding and polishing, and enabled it to perform its glorious duties as the grand essential part of a noble reflecting telescope!
The rationale of the strength of speculae cast in this metal-mould system, as compared with the treacherous brittleness of those cast in sand moulds, arises simply from the consolidation of the molten metal pool taking place first at the lower surface, next the metal base of the mould—the yet fluid alloy above satisfying the contractile requirements of that immediately beneath it; and so on in succession, until the last to consolidate is the top or upper stratum. Thus all risk of contractile tension, which is so dangerously eminent and inherent in the case of sand-mould castings, made of so exceedingly brittle an alloy as that of speculum metal, is entirely avoided. By the employment of these simple and effective improvements in the art of casting the specula for reflecting telescopes, and also by the contrivance and employment of mechanical means for grinding and polishing them, I at length completed my first 8-inch diameter speculum, and mounted it according to the Newtonian plan. I was most amply rewarded for all the anxious labour I had gone through in preparing it, by the glorious views it yielded me of the wonderful objects in the heavens at night. My enjoyment was in no small degree enhanced by the pleasure it gave to my father, and to many intimate friends. Amongst these was Sir David Brewster, who took a most lively and special interest in all my labours on this subject.
In later years I resumed my telescope-making enjoyments, as a delightful and congenial relaxation from the ordinary run of my business occupations. I constructed several reflecting-telescopes, of sizes from 10-inch to 20-inch diameter specula. I had also the pleasure of assisting other astronomical friends, by casting and grinding specula for them. Among these I may mention my late dear friend William Lassell, and my excellent friend Warren de la Rue, both of whom have indelibly recorded their names in the annals of astronomical science. I know of no subject connected with the pursuit of science which so abounds with exciting and delightful interest as that of constructing reflecting telescopes. It brings into play every principle of constructive art, with the inexpressibly glorious reward of a more intimate acquaintance with the sublime wonders of the heavens.
I communicated in full detail all my improvements in the art of casting, grinding, and polishing the specula of reflecting-telescopes to the Literary and Philosophical Society of Manchester, illustrating my paper with many drawings. But as my paper was of considerable length, and as the illustrations would prove costly to engrave, it was not published in the Society's Transactions. They are still, however, kept in the library for reference by those who take a special interest in the subject.
While assisting Mr. Maudsley in the execution of a special piece of machinery, in which it became necessary to have some holes drilled in rather inaccessible portions of the work in hand, and where the employment of the ordinary drill was impossible, it occurred to me that a flexible shaft, formed of a closely-coiled spiral of steel wire, might enable us to transmit the requisite rotary motion to a drill attached to the end of this spiral shaft. Mr. Maudsley was much pleased with the notion, and I speedily put it in action by a close coiled spiral wire of about two feet in length. This was found to transmit the requisite rotary motion to the drill at the end of the spiral with perfect and faithful efficiency. The difficulty was got over, to Mr. Maudsley's great satisfaction.
So far as I am aware, such a mode of transmitting rotary motion was new and original. The device was useful, and proved of essential service in other important applications. By a suitably close coiled spiral steel wire I have conveyed rotary motion quite round an obstacle, such as is indicated in the annexed figure. It has acted with perfect faithfulness from the winch handle at A to the drill at B. Any ingenious mechanic will be able to appreciate the value of such a flexible shaft in many applications.
Four years ago I saw the same arrangement in action at a dentist's operating-room, when a drill was worked in the mouth of a patient to enable a decayed tooth to be stopped. It was said to be the last thing out in "Yankee notions." It was merely a replica of my flexible drill of 1829.
This method is referred to, and drawings given, in the text, pp. 145-6.
This will be found described in the next and final chapter.
The fastening of wheels and belt pulleys to shafts, so as to enable them to transmit rotary motion, is one of the most frequently-recurring processes in the construction of machinery. This is best effected by driving a slightly tapered iron or steel wedge, or "key" as it is technically termed, into a corresponding recess, or flat part of the shaft, so that the wheel and shaft thus become in effect one solid structure.
The old mode of cutting such key-grooves in the eyes of wheels was accomplished by the laborious and costly process of chipping and filing. Maudsley's mortising machine, which he contrived for the Block machinery, although intended originally to operate upon wood, contained all the essential principles and details required for acting on metals. Mr. Richard Roberts, by some excellent modifications, enabled it to mortise or cut out the key-grooves in metal wheels, and this method soon came into general use. This machine consisted of a vertical slide bar, to the lower end of which was attached the steel mortising tool, which received its requisite up and down motion from an adjustable crank, through a suitable arrangement of the gearing. The wheel to be operated upon was fixed to a slide-table, and gradually advanced, so as to cause the mortising tool to take successive cuts through the depth of the eye of the wheel, until the mortise or key-groove had attained its required depth.
The only drawback to this admirable machine was that its service was limited in respect to admitting wheels whose half diameter did not exceed the distance from the back of the jaw of the machine to the face of the mortise tool; so that to give to this machine the requisite rigidity and strength to resist the strain on the jaw, due to the mortising of the key-grooves, in wheels of say 6 feet diameter, a more massive and cumbrous framework was required, which was most costly in space as well as in money.
In order to obviate this inconvenience, I designed an arrangement of a key-groove mortising machine. It was capable of operating upon wheels of any diameter, having no limit to its capacity in that respect. It was, at the same time, possessed, in respect of the principle on which it was arranged, of the power of taking a much deeper cut, there being an entire absence of any source of springing or elasticity in its structure. This not only enabled the machine to perform its work with more rapidity, but also with more precision. Besides, it occupied much less space in the workshop, and did not cost above one-third of the machines formerly in use. It gave the highest satisfaction to those who availed themselves of its effective services.
A comparison of Fig. 1 — which represents the general arrangement of the machine in use previous to the introduction of mine — with that of Fig. 2, may serve to convey some idea of their relative sizes. Fig. 1 shows a limit to the admission of wheels exceeding 6 feet diameter, Fig. 2 shows an unlimited capability in that respect.
One of the most numerous details in the structure of all classes of machines is the bolts which serve to hold the various parts together. As it is most important that each bolt fits perfectly the hole it belongs to, it is requisite that each bolt should, by the process of turning, be made perfectly cylindrical. In preparing such bolts, as they come from the forge, in order to undergo the process of turning, they have to be "centred;" that is, each end has to receive a hollow conical indent, which must agree with the axis of the bolt. To find this in the usual mode, by trial and frequent error, is a most tedious process, and consumes much valuable time of the workman as well as his lathe.
In order to obviate the necessity for this costly process, I devised the simple instrument, a drawing of which is annexed. The use of this enabled any boy to find and mark with absolute exactness and rapidity the centres of each end of bolts, or suchlike objects. All that was required was to place the body of the bolt in the V-shaped supports, and to gently cause it to revolve, pressing it longitudinally against the steel-pointed marker, which scratched a neat small circle in the true centre or axis of the bolt. This small circle had its centre easily marked by the indent of a punch, and the work was then ready for the lathe. This humble but really important process was accomplished with ease, rapidity, and great economy.
The desire to make the pistons of steam-engines of air-pump buckets of condensing engines perfectly steam and water tight has led to the contrivance of many complex and costly constructions for the purpose of packing them. When we take a common-sense view of the subject, we find that in most cases the loss resulting from the extra friction neutralises the expected saving. This is especially the case with the air-pump bucket of a condensing steam-engine, as it is in reality much more a water than an air pump. But when it is constructed with a deep well-fitted bucket, entirely without packing, the loss sustained by such an insignificant amount of leakage as may occur from the want of packing is more than compensated by the saving of power resulting from the total absence of friction.
The first condensing steam-engine, to which I applied an air-pump bucket, entirely without packing, was the forty-horse-power engine, which I constructed for the Bridgewater Foundry. It answered its purpose so well that, after twenty years' constant working, the air-pump cover was taken off, out of curiosity, to examine the bucket, when it was found in perfect order. This system, in which I dispensed with the packing for air-pump buckets of condensing steam-engines, I have also applied to the pistons of the steam cylinders, especially those of high-pressure engines of the smaller vertical construction, the stroke of which is generally short and rapid. Provided the cylinder is bored true, and the piston is carefully fitted, and of a considerable depth in proportion to its diameter, such pistons will be found to perform perfectly all their functions, and with a total absence of friction as a direct result of the absence of packing. By the aid of our improved machine tools, cylinders can now be bored with such perfect accuracy, and the pistons be fitted to them with such absolute exactness, that the small quantity of water which the steam always deposits on the upper side of the piston, not only serves as a frictionless packing, but also serves as a lubricant of the most appropriate kind. I have applied the same kind of piston to ordinary water-pumps, with similar excellent results.
The mode referred to consists in giving a rapid "switch" motion to a pencil upon a piece of paper, or a cardboard, or a smooth metal plate; and then cutting out the curve so produced, and employing it as a pattern or "template," to enable copies to be traced from it. When placed at equal distances, and at equal angles on each side of a central line, so as to secure perfect symmetry of form according to the nature of the required design, the beauty of these "instantaneous" curves, as I term them, arises from the entire absence of any sudden variation in their course. This is due to the momentum of the hand when "switching" the pencil at a high velocity over the paper. By such simple means was the beautiful curve produced, which is given above. It was produced "in a twinkling," if I may use the term to express the rapidity with which it was "switched." The chief source of the gracefulness of these curves consists in the almost imperceptible manner in which they pass in their course from one degree of curvature into another. I have had the pleasure of showing this simple mode of producing graceful curves to several potters, who have turned the idea to good account. The above illustrative figures have all been drawn from "templates" whose curves were "switched" in the manner of Fig. A.
Although the introduction of the planing machine into the workshops of mechanical engineers yielded results of the highest importance in perfecting and economising the production of machinery generally, yet, as the employment of these valuable machine tools was chiefly intended to assist in the execution of the larger parts of machine manufacture, a very considerable proportion of the detail parts still continued to be executed by hand labour, in which the chisel and the file were the chief instruments employed. The results were consequently very unsatisfactory, both as regards inaccuracy and costliness.
With the desire of rendering the valuable services of the Planing Machine applicable to the smallest detail parts of machine manufacture, I designed a simple and compact modification of it, such as should enable any attentive lad to execute all the detail parts of machines in so unerring and perfect a manner as not only to rival the hand work of the most skilful mechanic, but also at such a reduced cost as to place the most active hand workman far into the background. The contrivance I refer to is usually known as "Nasmyth's Steam Arm."
None but those who have had ample opportunities of watching the process of executing the detail parts of machines, can form a correct idea of the great amount of time that is practically wasted and unproductive, even when highly-skilled and careful workmen are employed. They have so frequently to stop working, in order to examine the work in hand, to use the straight edge, the square, or the calipers, to ascertain whether they are "working correctly." During that interval, the work is making no progress; and the loss of time on this account is not less than one-sixth of the working hours, and sometimes much more; though all this lost time is fully paid for in wages.
But by the employment of such a machine as I describe, even when placed under the superintendence of well-selected intelligent lads, in whom the faculty of good sight and nicety of handling is naturally in a high state of perfection, any deficiency in their physical strength is amply compensated by these self-acting machines.
The factory engine supplies the labour or the element of Force, while the machines perform their work with practical perfection. The details of machinery are thus turned out with geometrical accuracy, and are in the highest sense fitted to perform their intended purposes.
This will be found described summarily in the next and final chapter.
In the employment of Slide Turning Lathes, it is of great advantage to be able to reverse the motion of the Slide so as enable the turning tool to cut towards the Head of the Lathe or away from it, and also to be able to arrest the motion of the Slide altogether, while all the other functions of the lathe are continued in action. All these objects are attained by the simple contrivance represented in the annexed illustration. It consists of a lever E, moving on a stud-pin S, attached to the back of the head stock of the lathe T. This lever carries two wheels of equal diameter marked B and C. These wheels can pitch into a corresponding wheel A, fixed on the back end of the lay spindle. When the handle of the lever E is depressed (as seen in the drawing) the wheel B is in gear with wheel A, while C is in gear with the slide-screw wheel D, and so moves the slide (say from the Head Stock of the Lathe). On the other hand, when the lever E is elevated in position E", wheel B is taken out of gear with A, while C is put in gear with A, and B is put in gear with D; and thus the Slide is caused to move towards the Head Stock of the lathe. Again, where it is desired to arrest the motion of the Slide altogether, or for a time, as occasion may require, the lever handle is put into the intermediate position E', which entirely severs the communication between A and D, and so arrests the motion of the slide. This simple contrivance effectually served all its purposes, and was adopted by many machine tool-makers and engineers.
A frequent cause of undue friction and heating of rapidly-rotating machinery, arises from some inaccuracy or want of due parallelism between the rotating shaft or spindle and its bearing. This is occasioned in most cases by some accidental change in the level of the supports of the bearings. Many of the bearings are situated in dark places, and cannot be seen. There are others that are difficult of access—as in the case of bearings of screw-propeller shafts. Serious mischief may result before the heating of the bearing proclaims its dangerous condition. In some cases the timber work is set on fire, which may result in serious destruction.
In order to remove the cause of such serious mischief, I designed an arrangement of bearing, which enabled it, and the shaft working in it, to mutually accommodate themselves to each other under all circumstances, and thus to avoid the danger of a want of due and mutual parallelism in their respective axis. This arrangement consisted in giving to the exterior of the bearing a spherical form, so as, within moderate limits, to allow it to accommodate itself to any such changes in regard to mutual parallelism, as above referred to. In other cases, I employed what I may call Rocking centres, on which the Pedestal or "Plumber Block" rested; and thus supplied a self-adjusting means for obviating the evils resulting from any accidental change in the proper relative position of the shaft and its bearing. In all cases in which I introduced this arrangement, the results were most satisfactory.
In the case of the arms of Blowing Fans, in which the rate of rotation is naturally excessive, a spherical resting-place for the bearings enabled them to keep perfectly cool at the highest speed. This was also the case in the driving apparatus for machine tools, which is generally fixed at a considerable height above the machine. These spherical or self-adjusting bearings were found of great service. The apparatus, being generally out of convenient reach, is apt to get out of order unless duly attended to. But, whether or not, the saving of friction is in itself a reason for the adoption of such bearings. This may appear a technical matter of detail; but its great practical value must be my excuse for mentioning it.
The safety foundry ladle is described in the text, p. 209.
My invention was made at this early date, long before the attack by the steam-ram Merrimac upon the Cumberland, and other ships, in Hampton Roads, United States. I brought my plans and drawings under the notice of the Admiralty in 1845; but nothing was done for many years. Much had been accomplished in rendering our ships shot-proof by the application of iron plates; but it appeared to me that not one of them could exist above water after receiving on its side a single blow from an iron-plated steam ram of 2,000 tons. I said, in a letter to the Times, "As the grand object of naval warfare is the destruction by the most speedy mode of the ships of the enemy, why should we continue to attempt to attain this object by making small holes in the hull of the enemy when, by one single masterly crashing blow from a steam ram, we can crush in the side of any armour-plated ship, and let the water rush in through a hole, 'not perhaps as wide as a church door or as deep as a well, but it will do'; and be certain to send her below water in a few minutes."
I published my description of the steam ram and its apparatus in the Times of January 1853, and again addressed the Editor on the subject in April 1862. General Sir John Burgoyne took up the subject, and addressed me in the note at the foot of this page.  In June 1870, I received a letter from Sir E. J. Reed, containing the following extracts: "I was aware previously that plans had been proposed for constructing unarmoured steam rams, but I was not acquainted with the fact that you had put forward so well-matured a scheme at so early a date; and it has given me much pleasure to find that such is the case. It has been a cause both of pleasure and surprise to me to find that so long ago you incorporated into a design almost all the features which we now regard as essential to ramming efficiency — twin screws and moderate dimensions for handiness, numerous watertight divisions for safety, and special strengthenings at the bow. Facts such as these deserve to be put on record. . . . Meanwhile accept my congratulations on the great skill and foresight which your ram-design displays."
Collisions at sea unhappily afford ample evidence of the fatal efficiency of the ramming principle. Even iron-clad ships have not been able to withstand the destructive effect. The Vanguard and the Kurfurst now he at the bottom of the sea in consequence of an accidental "end-on" ram from a heavy ship going at a moderate velocity. High speed in a Steam Ram is only desirable when the attempt is made to overtake an enemy's ship; but not necessary for doing its destructive work. A crash on the thick plates of the strongest Iron-clad, from a Ram of 2,000 tons at the speed of four miles an hour, would drive them inwards with the most fatal results.
Described in text, p. 245.
For particulars and details, see Report of Torpedo Committee.
The late Mr. Wicksteed, engineer of the East London Water Company, having stated to me the inconvenience which had been experienced from the defects in respect of water-tightness, as well as the difficulty of opening and closing the valves of the main water-pipes in the streets, I turned my attention to the subject. The result was my contrivance of a double-faced wedge-shaped sluice-valve, which combined the desirable property of perfect water-tightness with ease of opening and closing the valve.
This was effected by a screw which raised the valve from its bearings at the first partial turn of the screw, after which there was no farther resistance or friction, except the trifling friction of the screw in its nut on the upper part of the sluice-valve. When screwed down again, it closed simultaneously the end of the entrance pipe and that of the exit pipe attached to the valve case in the most effective manner.
Mr. Wicksteed was so much pleased with the simplicity and efficiency of this valve, that he had it applied to all the main pipes of his Company. When its advantages became known, I received many orders from other water companies, and the valves have since come into general use. The prefixed figure will convey a clear idea of the construction. The wedge form of the double-faced valve is conspicuous as the characteristic feature of the arrangement.
Being under the impression that there are many processes in the manufacturing arts, in which a perfectly controllable compressing power of vast potency might be serviceable, I many years ago prepared a design of an apparatus of a very simple and easily executed kind, which would supply such a desideratum. It was possessed of a range of compressing or squeezing power, which far surpassed anything of the kind that had been invented. As above said, it was perfectly controllable; so as either to yield the most gentle pressure, or to possess the power of compressing to upwards of twenty thousand tons; the only limit to its strength being in the materials employed in its construction.
The principle of this enormously powerful compressing machine is similar to that of the Hydraulic Press; the difference consisting principally in the substitution of what I term a Hydraulic Mattress in place of the cylinder and ram of the ordinary hydraulic press. The Hydraulic Mattress consists of a water-tight vessel or flat bag formed of half-inch thick iron or steel plates securely riveted together; its dimensions being 15 feet square by 3 feet deep, and having semicircular sides, which form enables the upper flat part of the Mattress to rise say to the extent of 6-inches, without any injury to the riveted joints, as such a rise or alteration of the normal form of the semicircular sides would be perfectly harmless, and not exceed their capability of returning to their normal curve when the 6-inch rise was no longer necessary, and the elevating pressure removed.
The action of this gigantic press is as follows. The Mattress A A having been filled with water, an additional quantity is supplied by a force pump, capable of forcing in water with a pressure of one ton to the square inch; thus acting on an available surface of at least 144 square feet surface — namely, that of the upper flat surface of the Mattress. It will be forced up by no less a pressure than twenty thousand tons, and transfer that enormous pressure to any article that is placed between the rising table of the press and the upper table. When any object less thick than the normal space is required to receive the pressure, the spare space must be filled with a suitable set of iron flat blocks, so as to subject the article to be pressed to the requisite power.
As before stated, there may be many processes in the manufacturing arts, in which such an enormous pressure may be useful; and this can be accomplished with perfect ease and certainty. I trust that this account of the principles and construction of such a machine may suggest some employment worthy of its powers. In the general use of the Mattress press, it would be best to supply the pressure water from an accumulator, which should be kept constantly full by the action of suitable pumps worked by a small steam-engine. The great press would require the high-pressure water only now and then; so that it would not be necessary to wait for the small pump to supply the pressure water when the Mattress was required to be in action.
The letter X shows how Screws are frequently made when tapped in the old mode; the letter T as they are always made when the Tapping Square is employed.
In executing an order for twenty locomotive engines for the Great Western Railway Company, there was necessarily a repetition of detail parts. Many of them required the labour of the most skilful workmen, as the parts referred to did not admit of their being executed by the lathe or planing-machine in their ordinary mode of application. But the cost of their execution by hand labour was so great and the risk of inaccuracy was so common (where extreme accuracy was essential), that I had recourse to the aid of special mechanical contrivances and machine tools for the purpose of getting over the difficulty. The annexed illustration has reference to only one class of objects in which I effected great saving in the production, as well as great accuracy in the work. It refers to a contrivance for producing by the turning-lathe the eighty bands of the eccentrics for these twenty engines. Being of a segmental form, but with a projection at each extremity, which rendered their production and finish impossible by the ordinary lathe, I bethought me of applying what is termed the mangle motion to the rim of a face plate of the lay, with so many pins in it as to give the required course of segmental motion for the turning tool to operate upon, between the projections C C in the illustration. I availed myself of the limited to-and-fro horizontal motion of the shaft of the mangle motion wheel, as it, at each end of the row of pegs in the face plate (when it passes from the exterior to the interior range of them) in giving the feed motion to the tool in the slide rest, "turned" the segmental exterior of the eccentric hoops. This it did perfectly, as the change of position of the small shaft occurred at the exact time when the cut was at its termination, — that being the correct moment to give the tool "the feed," or advance for the taking of the next cut. The saving, in respect to time, was 10 to 1 in comparison with the same amount of work done by hand labour while the "truth" or correctness of the work done by this handy little application of the turning-lathe was absolutely perfect. I have been the more particular in my allusion to this contrivance, as it is applicable to any lathe, and can perform work which no lathe without it can accomplish. The unceasing industry of such machines is no small addition to their attractions, in respect to the production of unquestionably accurate work.
Described in text, p. 274.
The chief novelty in this swivel joint is the manner in which the packing of the joints is completely inclosed, and so rendering them perfectly and permanently watertight.
The principle on which Blowing Fans act, and to which they owe their efficiency, consists in their communicating Centrifugal action to the air within them. In order to obtain the maximum force of blast, with the minimum expenditure of power, it is requisite so to form the outside rim of the Fan-case as that each compartment formed by the space between the ends of the blades of the Fan shall in its course of rotation possess an equal facility of exit for the passage of the air it is discharging. Thus, in a Fan with six blades, the space between the top of the blades and the case of the Fan should increase in area in the progressive ratios of 1-2-3-4-5-6. If a Fan be constructed on this common-sense principle, we shall secure the maximum of blast from the minimum of driving power. And not only so; but the humming sound, — so disagreeable an accompaniment to the action of the Fans (being caused by the successive sudden escape of the air from each compartment as it comes opposite the space where it can discharge its confined block of air), will be avoided. When the outer case of a Fan is formed on the expanding or spiral principle, as above described, all these important advantages will attend its use. As the inward current of air rushes in at the circular openings on each side of the Fan-case, and would thus oppose each other if there was a free communication between them, this is effectually obviated by forming the rotating portion of the fan by a disc of iron plate, which prevents the opposite in-rushing currents from interfering with each other, and at the same time supplies a most substantial means of fastening the blades, as they are conveniently riveted to this central disc. On the whole, this arrangement of machinery supplies a most effective "Noiseless Blowing Fan."
The frequency of disastrous colliery explosions induced me to give my attention to an improved method for ventilating coalmines. The practice then was to employ a furnace, placed at the bottom of the upcast shaft of the coal-pit, to produce the necessary ventilation. This practice was highly riskful. It was dangerous as well as ineffective. It was also liable to total destruction when an explosion occurred, and the means of ventilation were thus lost when it was most urgently required.
The ventilation of mines by a current of air forced by a Fan into the workings, had been proposed by a German named George Agricola, as far back as 1621. The arrangement is found figured in his work entitled De Re Metalica, p. 162. But in all cases in which this system of forcing air through the workings and passages of a mine has been tried, it has invariably been found unsuccessful as a means of ventilation.
As all rotative Blowing Fans draw in the air at their centres, and expel it at their circumference, it occurred to me that if we were to make a communication between the upcast shaft of the mine and the centre or suctional part of the Fan closing the top of the upcast shaft, a Fan so arranged would draw out the foul air from the mine, and allow the fresh air to descend by the downcast shaft, and so traverse the workings. And as a Suction Fan so placed would be on the surface of the ground, and quite out of the way of any risk of injury—being open to view and inspection at all times — we should thus have an effective and trustworthy means for thorough ventilation.
Having communicated the design for my Direct Action Suction Fan for coal-pit ventilation to the Earl Fitzwilliam, through his agent Mr. Hartop, in 1850, his lordship was so much pleased with it that I received an order for one of 14 feet diameter, for the purpose of ventilating one of his largest coal-pits. I arranged the steam-engine which gave motion to the large Fan, so as to be a part of it; and by placing the crank of the engine on the end of the Fan-shaft, the engine transferred its power to it in the most simple and direct manner. The high satisfaction which this Ventilating Fan gave to the Earl, and to all connected with his coal-mines, led to my receiving orders for several of them. I took out no patent for the invention, but sent drawings and descriptions to all whom I knew to be interested in coal-mine ventilation. I read a paper on the subject, and exhibited the necessary drawings, at the meeting of the British Association at Ipswich in 1851. These were afterwards published in the Mining Journal. The consequence is that many of my Suction Ventilating Fans are now in successful action at home and abroad.
One of the most important processes in connection with the production of the details of machinery, and other purposes in which malleable iron is employed, is that termed welding, namely, when more or less complex forms are, so to speak, "built up" by the union of suitable portions of malleable iron united and incorporated with each other in the process of welding. This consists in heating the parts which we desire to unite to a white heat in a smith's forge fire, or in an air furnace, by means of which that peculiar adhesive "wax-like" capability of sticking together is induced, so that when the several parts are forcibly pressed into close contact by blows of a hammer, their union is rendered perfect.
But as the intense degree of heat which is requisite to induce this adhesive quality is accompanied by the production of a molten oxide of iron that clings tenaciously to the white-hot surfaces of the iron, the union will not be complete unless every particle of the adhesing molten scoriae is thoroughly discharged and driven out from between the surfaces we desire to unite by welding. If by any want of due care on the part of the smith, the surfaces be concave or have hollows in them, the scoriae will be sure to lurk in the recesses, and result in a defective welding of a most treacherous nature. Though the exterior may display no evidence of the existence of this fertile cause of failure, yet some undue or unexpected strain will rend and disclose the shut-up scoriae, and probably end in some fatal break-down.
The annexed figures will perhaps serve to render my remarks on this truly important subject more clear to the reader. Fig. 1 represents an imperfectly prepared surface of two pieces of malleable iron about to be welded. The result of their concavity of form is that the scoriae are almost certain to be shut up in the hollow part, as the pieces will unite first at the edges and thus include the scoria, which no amount of subsequent hammering will ever dislodge. They will remain lurking between, as seen in Fig. 2. Happily, the means of obviating all such treacherous risks are as simple as they are thoroughly effective. All that has to be done to render their occurrence next to impossible is to give to the surfaces we desire to unite by welding a convex form as represented in Fig. 3; the result of which is that we thus provide an open door for the scoriae to escape from between the surfaces, as these unite first in the centre, as due to the convex form, and then the union proceeds outwards, until every particle of scoriae is expelled, and the union is perfectly completed under the blows of the hammer or other compressing agency. Fig. 4 represents the final and perfect completion of the welding, which is effected by this common sense and simple means, that is, by giving the surfaces a convex form instead of a concave one.
When I was called by the Lords of the Admiralty in 1846 to serve on a Committee, Fig. 4. the object of which was to investigate the causes of failure in the wrought-iron smith work of the navy, many sad instances came before us of accidents which had been caused by defective welding, especially in the vitally important articles of Anchors and Chain Cables. In the case of the occasional failure of chain cables, the cause was generally assigned to defective material; but circumstances led me to the conclusion that it was a question of workmanship or maltreatment of what I knew to be of excellent material. I therefore instituted a series of experiments which yielded conclusive evidence upon the subject; and which proved that defective welding was the main and chief cause of failure. In order to prove this, several apparently excellent cables were, by the aid of "the proving machine," pulled to pieces, link by link, and a careful record was kept of the nature of the fracture. The result was, that out of every 100 links pulled asunder 80 cases clearly exhibited defective welding; while only 20 were broken through the clear sound metal. This yielded a very important lesson to those specially concerned.
Having been on several occasions called to investigate the causes of steam boiler explosions, my attention was naturally directed to the condition of the Safety Valve. I found the construction of them in many cases to be defective in principle as well as in mechanical details; resulting chiefly from the employment of a conical form in the valve, which necessitated the use of a guide spindle to enable it to keep in correct relative position to its corresponding conical seat, as seen at A in Fig. 1. As this guide spindle is always liable to be clogged with the muddy deposit from the boiling water, which yields a very adhesive encrustation, the result is a very riskful tendency to impede the free action of the Safety Valve, and thereby prevent its serving its purpose.
With a view to remove all such causes of uncertainty in the action of this vitally important part of a steam boiler I designed a Safety Valve, having a spherical valve and corresponding seat, as seen in B C, Fig. 2. This form of Safety Valve had the important property of fitting to its bearing-seat in all positions, requiring no other guide than its own spherical seat to effect that essential purpose. And as the weight required to keep the valve closed until the exact desired maximum pressure of steam has been attained, is directly attached to the under side of the valve by the rod, the weight, by being inside the boiler, is placed out of reach from any attempt to tamper with it.
The entire arrangement of this Safety Valve is quite simple. It is free from all Lever Joints and other parts which might become clogged; and as there is always a slight pendulous motion in the weight by the action of the water in the boiler, the spherical surfaces of the valve and its seat are thus ever kept in perfect order. As soon as the desired pressure of steam has been reached, and the gravity of the weight overcome, the valve rises from its seat, and gives perfectly free egress to any farther accumulation of steam. It is really quite a treat, in its way, to observe this truly simple and effective Safety Valve in action. After I had contrived and introduced this Safety Valve, its valuable properties were speedily acknowledged, and its employment has now become very general.
One of the most tedious and costly processes in the execution of the detail parts of machinery is the cutting out of Cottar Slots in piston rods, connecting rods, and key recesses in shafts. This operation used to be performed by drilling a row of holes through the solid body of the object, and then chipping away the intermediate metal between the holes, and filing the rude slot, so produced, into its required form. The whole operation, as thus conducted, was one of the most tedious and irksome jobs that an engineer workman could be set to, and could only be performed by those possessed of the highest skill. What with broken chisels and files, and the tedious nature of the work, it was a most severe task to the very best men, not to speak of the heavy cost in wages.
In order to obviate all these disadvantages, I contrived an arrangement of a drilling machine, with a specially formed drill, which at once reduced the process to one of the easiest conducted in an engineer's workshop. The "special" form of the Drill consisted in the removal of the centre portion of its flat cutting face by making it with a notch O. This enabled it to cut sideways, as well as downwards, and thus to cut a slit or oblong hole. No labour, as such, was required; but only the intelligent superintendence of a lad to place the work in the machine, and remove it for the next piece in its turn. The machine did the labour, and by its self-action did the work in the most perfect manner.
I may further mention that the arrangement of the machine consisted in causing the object to traverse to and fro in a straight line, of any required length, under the action of the drill. The traversing action was obtained by the employment of an adjustable crank, which gave the requisite motion to a slide table, on which the work was fastened. The "feed" downwards of the drill was effected by the crank at the moment of its reversing the slide, as the drill reached the end of the traverse; and, as there is a slight pause of the traverse at each end of it, the "feed" for the next cutting taking place at that time, the drill has the opportunity given to perfect its cut ere it commences the next cutting traverse in succession. This action continues in regular course until the drill makes its way right through the piece of work under its action; or can be arrested at any required depth according to the requirements of the work. Soap and water as a lubricator continues to drop into the recess of the slot, and is always in its right place to assist the cutting of the drill.
As before said, the entire function of this most effective machine tool is self-acting. It only required an intelligent lad or labourer to attend to it; and as there was ample time to spare, the superintendence of two of these machines was quite within his ability. The rates of the productive powers of this machine, as compared with the former employment of hand labour, was at least ten to one; to say nothing of the superior quality of the work executed.
Such were the manifold advantages of this machine, that its merits soon became known and appreciated; and although I had taken out no patent for it, we always had an abundance of orders, as it was its own best advertisement.
This engine is of great simplicity and get-at-ability of parts. It is specially adapted for screw-propelled steamships, and many other purposes. It is now in very general use. The outline is given on the next page.
Dr. Faraday having applied to me to furnish him, for one of his lectures at the Royal Institution, with some striking example of the Power of Machinery in overcoming the resistance to penetration in the case of some such material as cold malleable iron, it occurred to me to apply the tranquil but vast power of a hydraulic press to punch out a large hole in a thick cake of malleable iron. Knowing that my excellent friend John Hick had in his works at Bolton one of the most powerful hydraulic presses then existing, contrived and constructed by his ingenious father, the late Benjamin Hick, I proceeded to Bolton, and explained Dr. Faraday's requirement, when, with his usual liberal zeal, Mr. Hick at once placed the use of his great hydraulic press at my service.
Having had a suitable cake of steam-hammered malleable iron given to me for the purpose in question, by my valued friend Thomas Lever Rushton of the Bolton Ironworks, we soon had the cake of iron placed in the great press. It was 5 inches thick, 18 inches long, and 15 inches wide. Placing a cylindrical coupling box of cast-iron on the table of the press, and then placing the thick cake of iron on it, and a short cylindrical mass of iron (somewhat of the size and form of a Stilton Cheese) on the iron cake, — the coupling box acting as the Bolster of the extemporised punching machine, the press was then set to work. We soon saw the Stilton Cheese-like punch begin to sink slowly and quietly through the 5-inch thick cake of iron, as if it had been stiff clay. The only sound heard was when the punched-out mass dropped into the recess of the coupling below. Such a demonstration of tranquil but almost resistless power of a hydraulic press had never, so far as we were aware, been seen before. The punched cake of iron, together with the punched-out disc, were then packed off to Faraday; and great was his delight at having his request so promptly complied with. Great also was the wonder of his audience when the punched plate was placed upon the lecture table.
This feat of Benjamin Hick's great hydraulic press set me a-thinking. I conceived the idea that the application of hydraulic press power might serve many similar purposes in dealing with ultra thick plates or bar iron, — such as the punching out of holes, and cutting thick bars and plates into definite shapes, as might be required. I suggested the subject to my friend Charles Fox, head of the firm of Fox, Henderson, and Co. He had taken a large contract for a chain bridge, the links of which were to be of thick flat iron bars, with the ends broadened out for the link-pins to pass through. He had described to me the trouble and cost they had occasioned him in drilling the holes, and in cropping the rude-shaped ends of the bars into the required form. I advised him to try the use of the hydraulic press as a punching-machine, and also as a cutting-mad-line to dress the ends of the great links. He did so in due time, and found the suggestion of great service and value to him in this, and in other cases of a similar kind. The saving of cost was very great, and the work was much more perfect than under the former system.
This is so arranged that the observer can direct the Telescope and view an object in any part of the heavens without moving from his seat, which is attached to the turn-table. For explanations, see text, p. 351.
This is a very valuable tool. It requires only one attendant. It is especially useful as regards efficiency and economy. It will be sufficiently understood by mechanical engineers from the annexed drawings.
This was the "pioneer" of the Bessemer process. See Bessemer correspondence, p. 365.
This Rolling Mill consists of two combined steam-engines, acting on cranks at right angles, the reversing of the rolls being effected by the link motion. The requisite rolling power is obtained by suitable wheel and pinion gear, so as to be entirely independent of the momentum of a fly-wheel, which is entirely dispensed with.
This invention was first brought into use by Mr. Ramsbotham at the Crewe works of the London and North Western Railway. It soon came into general use, especially for rolling long and heavy bars and plates. It enables the workmen to "see-saw" these ponderous objects, and pass them to and fro through the rolls with the utmost ease, to the great saving of heat, time, and labour.
Besides these contrivances and methods of accomplishing mechanical objects, I have on several occasions read papers, prepared drawings, and given suggestions, out of which have come so-called "inventions" made by others. For instance, at the meeting of the British Association in Liverpool in 1854, I read a paper and exhibited drawings before the Mechanical Science Section, on my method of drilling tunnels through hard rock. The paper and drawings excited considerable interest among the railway engineers who were present. I afterwards met Mr. George Newmann, C.E., who consulted me on the same subject. Several years after (21st April 1863) I received the following letter from him:—
"DEAR SIR — Some few years ago, I had the pleasure of spending an evening in your company at my relative's (Mr. C. Withington) house at Pendleton. As I was then Engineer to the Victor Emmanuel Railway, and had made a survey of the Mont Cenis for the purpose of the Tunnel, I consulted you as to the application of the machinery for that work. You suggested the driving of drills in a manner similar to a piston-rod, with other details. On my return to Savoy, I communicated these ideas to Mr. Bartlett, the contractor's agent, and I recommended him to get a small trial machine made. This he had done in a few months, and then he claimed the whole idea as his own. The system has since been carried out (see Times, 4th April 1863) by compressed air instead of steam. I call your attention to this, as you may contradict, if you think proper, the assertion in the article above mentioned, that the idea originated with Bartlett."
I did not, however, contradict the assertion. I am glad that my description and drawings proved in any way useful towards the completion of that magnificent work, the seven-mile tunnel under Mont Cenis.
In like manner, I proposed the use of Chilled Cast-Iron Shot at a meeting of the Mechanical Science Section of the British Association, held at Cambridge in October 1862. Up to that time hardened steel shot had been used to penetrate thick iron plates, but the cost was excessive, about £30 a ton. I proposed that Chilled Cast-Iron should be substituted; it was more simple and inexpensive. Considerable discussion took place on the subject; and Sir William Fairbairn, who was President of the Section, said that "he would have experiments made, and he hoped that before the next meeting of the Association, the matter would be proved experimentally." A brief report of the discussion is given in the Times of the 7th October, and in the Athenaeum of the 18th October, 1862. Before, however, the matter could be put to the test of experiment, Major Palliser had taken out his Patent for the invention of Chilled Cast-Iron Shot, in May 1863, for which he was afterwards handsomely rewarded.
I do not wish to "grasp" at any man's inventions, but it is right to claim my own, and to state the facts. The discussion above mentioned took place upon a paper read by J. Aston, Esq., Q.C., who thus refers to the subject in his letter to me, dated the 7th January 1867:—
"I perfectly remember the discussion which took place at the meeting of the British Association at Cambridge in 1862, upon the material proper to be used as projectiles. The discussion arose after a paper had been read by me in the Mechanical Section upon "Rifled guns and projectiles adapted for attacking armour plates." The paper was, I think, printed by the Association in their Report for 1862. You spoke, I believe, at some length on the occasion and I recollect that you surprised and much interested all who were present, by strenuously urging the use of Chilled Cast-iron for shot and shell, intended for penetrating armour plates.
"Having embraced all opportunities, and I had many at that time, of ascertaining all that was done in the way of improving rifled projectiles, I entertained a very strong opinion that experiments had shown that ordinary cast-iron was, as compared with steel, of very little value for shot and shell to be used against iron plates. For that reason, I remember I took an opportunity, after the termination of the discussion, in which you held your own against all comers in favour of chilled cast-iron, of questioning you closely on the subject, and you gave me, I admitted, good reason for the opinion you expressed. You also urged me to cause a trial to be made of chilled cast iron for shell, such as I had shown to the section, and which (in hardened steel shot) had been fired by Mr. Whitworth through thick iron plates. This I had not an opportunity of doing. Term began soon after, and Temple occupations then took up all my time.
"There can be no doubt whatever that any one who may claim to have been before you in teaching the public the use of Chilled Cast-Iron for projectiles intended to penetrate iron plates, must give proof of having so done prior to your vigorous advocacy of that material at the Cambridge Meeting in 1862. — Yours very sincerely, J. ASTON."
In another letter, Mr. Aston says— "It is quite right of you to assert your claim to that which in fact belongs to you." I did not, however, assert my claim; and, with these observations and extracts, I leave the matter, stating again the fact that my public communication of the invention was made in October 1862; and that the patent for the invention was taken out by Major Palliser in May 1863.
I have only mentioned the more prominent of my inventions and contrivances. Had I described them fully I should have required another volume. I have the satisfaction to know that many of them have greatly advanced the progress of the mechanical arts, though they may not be acknowledged as mine. I patented very few of my inventions. The others I sowed broadcast over the world of practical mechanics. My reward is in the knowledge that these "children of my brain" are doing, and will continue to do, good service in time present and in time to come.
In mechanical structures and contrivances, I have always endeavoured to attain the desired purpose by the employment of the Fewest Parts, casting aside every detail not absolutely necessary, and guarding carefully against the intrusion of mere traditional forms and arrangements. The latter are apt to insinuate themselves, and to interfere with that simplicity and directness of action which is in all cases so desirable a quality in mechanical structures. PLAIN COMMON SENSE should be apparent in the general design, as in the form and arrangement of the details; and a general character of severe utility pervade the whole, accompanied with as much attention to gracefulness of form as is consistent with the nature and purpose of the structure.
A. Chill plate of cast iron turned to the curve of the speculum. B. Turned hoop of wrought iron with opening at 0. C. Pouring pocket. D. Counterpoise, by which the chill plate is tilted up. The largest figure in the engraving is the annealing tub of cast iron filled with sawdust, where the speculum is placed to cool as slowly as possible.