William Gravatt
William Gravatt (1806-1866)
1828 became a full member of the Inst of Civil Engineers
1867 Obituary [1]
MR. WILLIAM GRAVATT was born at Gravesend on the 14th of July, 1806.
In January, 1822, his father, the late Colonel Gravatt, of the Royal Engineers, Inspector of the Royal Military Academy at Woolwich, wrote to the late Mr. Bryan Donkin:- 'My son has been brought up to know that he must trust to his own resources for advancement in life. Throwing as far as I can from me the partiality of a father, I must yet be permitted to say that his habits are peculiarly suited for the attainment of the duties of your noble profession, since, to a good classical education he joins a knowledge of mathematics seldom attained at his years, including the practical parts of perspective, and the drawing of plans, elevations, and sections; he has also a most determined bias to whatever relates to machinery, which last I attribute to his having made the steam and other engines in this arsenal the objects of his contemplation.'
At the early age of fifteen years, he already showed an appreciation of delicate, mechanical manipulation, as well as an aptitude for mathematical investigation, for both of which he was in after life very remarkable. Shortly after he was placed with Mr. Donkin, a small wager was laid between young Gravatt and a fellow apprentice, that the latter could not, in a given time, unwind a given length of string from a stick planted in the ground by walking round it. Gravatt’s winning the wager led him to get out a formula for determining the distance walked round the fixed stick, which his friend the late Professor Barlow found to be correct, and remarked that the same thing happened to be then under consideration by the cadets of the Royal Academy.
During his apprenticeship under Mr. Donkin he not only went though the usual routine of mechanical engineering, but he was likewise initiated into those scientific acquirements, the value of which, as essential to the professional status of a Civil Engineer, is now more properly recognized, and of which he never lost sight.
At this time began the intimacy with Mr. Troughton and Dr. Wollaston, which continued until their deaths. Through the former he may be said to have been connected by tradition with the father of English Engineers, as the following anecdote will show. At one of Gravatt’s frequent visits to Troughton’s back parlour, in Fleet Street, he fell into conversation, during her brother’s absence, with Miss Troughton, who described the personages therein admitted. 'They all praised her brother' she said, 'save one, a short man, with a grey coat;' and for this she was inclined 'to eye him askant.' He, however, came one day 'to bid Edward his last farewell,' and, at parting, was observed to be in tears. As soon as he was gone, 'Now I know,' said the sister to her brother, 'why he never praised you. ’Twas because he loved you.' This man was John Smeaton.
On leaving the works of Mr. Donkin he was placed under Mr., afterwards Sir Isambard Brunel, who, before Gravatt’s apprenticeship expired, 'considered that he was a competent person to attend to the management of 'the shield,’ in particular, and, in general, to the machinery belonging to the Thames Tunnel.'
He frequently remained in the frames all night, and more than once, when Mr. I. E. Brunel was incapacitated by sickness, he stayed on duty for thirty-eight hours, spending those needed for rest at the bedside of his friend.
'On the 5th of March, 1828, silver medals were voted by the Royal Humane Society to Mr. I. K. Brunel and Mr. William Gravatt for having hazarded their own lives to preserve those of their fellow-creatures.' To the latter was presented, by the two directors, Mr. R. H. Marten and Mr. R. P. Harris, a gold ring, as 'A memorial of the events of the 27th of June, 1827, and of his humane, prompt, and efficient help in rescuing them from a perilous situation' during a survey by boat of the interior of the Thames Tunnel after an irruption of the river.
In 1832 he became a Fellow of the Royal Society and of the Royal Astronomical Society, and in the proceedings of both Societies he took an active interest. 'I used to meet,' says Professor De Morgan, 'two Engineers at the Society, one military and one civil, who were very curious about questions of principle in mathematics. The first was General Colby, the second was Mr. Gravatt, who was quick to see, and, certainly, a mathematician of the higher branches. A long time ago he told me that he had derived so much benefit from my work on the Differential Calculus that he must insist on subscribing, as a testimonial of the instruction he had received, to some charity; and he requested me to name an institution. I thought he was in joke, and laughed; but he convinced me he was in earnest, at which I laughed still more. I refused to name any charity, and, as I thought, the matter ended. But, a few days after, I actually received a subscriber’s voting-paper for some orphan asylum, which he requested me to fill up in my own way out of the list of candidates, and forward: which I did. There was a curious eccentricity about the method, but it showed a real sense of benefit received; and a person who could have any right to the feeling from so extensive a work on the higher mathematics as my Differential Calculus, must either have been a person who could flatter himself he understood what he did not - a very unlikely thing in so clear-headed a person - or must have had a true understanding of the contents. And this was the impression I derived from other conversations.'
Upon the stoppage of the Thames Tunnel works in 1832, he was, by the recommendation of Mr. Donkin, appointed Engineer to the Calder and Hebble Navigation. Here he commenced his first works, in the shape of several bridges across the river, the arches of which were remarkable for their stability and cheapness; in these he was, perhaps, the first to adopt a principle equivalent to that since successfully applied to suspension bridges, i.e., the combination of local rigidity with the distributed support which the curvature of the flexible chain supplies. Thus, while the general curvature of the chain or arch sustains the dead load in equilibrio, the addition of longitudinal stiffness to the structure meets the non-equilibrated stress due to unequal or travelling load.
The rise, in Gravatt’s bridges, of necessity small, being in the ratio of 4 to a 100 span, he obtained the help of rigidity by an arrangement analogous rather to that proposed by Mr. Cowper, in which the suspending chain, instead of being flexible, is formed of plate iron, so as to possess in the requisite degree the rigidity of a plate or box-girder, than to that of Roebling or Barlow, in which the local rigidity is supplied by the structure of the roadway.
The platform of the roadway was laid throughout, on the back of a pair of arched girders, each of which consisted of several layers of timber bolted together, with hard wood keys interposed between the contiguous layers buried half in each, near the bolts, so as to prevent the surfaces from sliding, when pressure had to be obliquely transmitted from layer to layer. In such a structure the stress due to dead load must be throughout compressional, while that due to travelling load may be resolved into:- l. Compressional stress throughout the length of the girder; and, 2. Bending moment, having a local distribution appropriate to the position of the load, and producing tension along the inner, and compression along the outer surface of the girder, or vice versa, according as the curvature which it tends to induce is of a downward or upward character. Under these combined stresses, as they existed in the Gravatt Bridge, it is only when the travelling load rests on a certain region of either haunch, that actual tensional stress is developed ; and then only in the fibres nearer to the inner or outer surface of the girder. Hence, in the first place, in arranging the layers, lengths of which his girders consisted, Mr. Gravatt adopted such dimensions that no break of joint in the inner or outer layers should occur within the region in which actual tensional stress could be developed. Thus, the central part of the girder, forming the, region of the neutral axis, and therefore but little affected by the forces which belong to 'bending moment,' is, in virtue of its position, exempt from that excess of compressional strain which its inner and outer surfaces along the haunches are occasionally called on to endure. And hence, in the second place, in putting the work together, Mr. Gravatt so arranged the combinations that central layers should, prior to the loading of the bridge, already experience a considerable amount of compression, and should thus, when in place, relieve the inner and outer surface of some portion of that excess of compression which, under the circumstances, tends occasionally to fall on them.
In other words : 1. The stress on the equilibrated arched girder loaded throughout is compressional; 2. When unequally loaded, and the one munch thereby depressed, the other elevated, the under side of one is a little in tension, and its top a great deal in compression; while the other, or opposite haunch, has its under side much in compression, and its top little in tension; in each case, if the centre line, being almost unaflected, be previously thrown into strong compression in each haunch, then, the excess of tension in either, being thrown on the central part in both, is corrected. Now, Mr. Gravatt, in the act of putting the parts of his cambered girder together, developed a permanent stress on some of them, and, by this means, got out of the material the maximum of work.
By Mr. H. R. Palmer he was employed in examining the country for the original scheme of the London and Dover Railway. During the early period of railway construction he devised a level, which generally bears his name, but which he called the ‘dumpy,’ and also the level-staff, which is now universally employed, but which is not generally known to have been introduced by him.
Those whose experience in levelling has been acquired by help of the compact and simple instruments now universally in use, can hardly conceive the range of the step which was made in advance, when these improved appointments, at once matured to a degree which left little room for improvement, were introduced by Mr. Gravatt above thirty years ago. Mr. Troughton had, indeed, already substituted for the cumbrous Y level, with its easily disturbed adjustments, an instrument pretty firmly mounted, and having adjustments of a formal character. But the telescope, from its large focal length and relatively small aperture, was wanting in compactness and in light; and no improvement had yet been made on the old-fashioned staff, with its sliding vane which had to be adjusted to the intersection of the horizontal web, under signal from the observer, by the staff-holder, on whose care in making the adjustment, and in preserving it till the stag had been handled and read by the observer, the veracity of the result materially depended.
Mr. Gravatt at once grasped the idea that, with a decent telescope and legibly divided staff, the observer could independently read off his own observations while the staff was in position, and he accordingly originated the character of division now universally in use. And applying to the subject his masterly knowledge of theoretical and practical optics, he so arranged the optical details of the telescope as to obtain, with an object glass of large aperture and short focus, breadth and flatness of field as well as excellent achromatization and definition. For these valuable improvements a Telford Medal was awarded to him by the Institution of Civil Engineers.
He likewise contrived a pocket instrument, which he called a 'nadir,' by means of which, and a common box-sextant, without the aid of an assistant or a level-staff, he carried lines of trial levels through districts where the opposition of land-owners or other obstacles rendered the traversing of the country, save by the highways, impracticable.
After the rejection of the first Great Western Railway Bill, and the passing of that of the Southampton Railway, which latter, together with the Bath and Basing line, he helped to oppose, in 1834, he was employed by the late Mr. Brunel to survey a line of railway from Cardiff to Merthyr Tydfil and Dowlais; and, from the passing of the Great Western Railway Act, he was engaged in designing bridges for the first contracts for that line.
In 1835, he was engaged by Mr. Brunel to superintend the parliamentary surveys and to co-operate with him in tracing the line for the Bristol and Exeter Railway. This task exhibited his extraordinary and well-known powers of endurance; the whole work, extending over 75 miles, being begun and ended in about a month. The ability with which it was carried out was proved by the permanent works being executed throughout within the limit of the 100 yards on either side of the line laid down on the original parliamentary plans; in other words, no further deviation therefrom was called for during the construction of the railway.
Whilst carrying out the works of this line, of which he had been appointed the Acting Engineer by Mr. Brunel, he was, on his own account, Engineer to the canalization of the River Parret to Langport, where he constructed a stone bridge ; and, at Bristol, he designed and superintended the erection of the St. Phillip’s drawbridge, the stone piers of which were built on shore in caissons, then launched and sunk in their places.
During the railway mania of 1845-6, Mr. Gravatt unwisely accepted the post of Engineer to several lines, which turned out mere bubbles, and by whose promoters he was not only left without professional remuneration, but he was saddled with the cost of the surveys and preliminary charges. His position was thereby, not only then, but prospectively, affected ; and during the rest of his days he suffered more or less from those severe disappointments.
In 1850 he was, on account of his well-known mathematical and mechanical acquirements, selected to design and to superintend the construction of an Achromatic Telescope, which was to have been the largest that had hitherto been produced. For the object glass, the refractive-index and dispersive-ratio of the flint and crown-glass parts were determined by a series of careful experiments; and from the data thus acquired the curves of the two lenses were calculated for a combined focal length of 76 feet. The first observation made showed the divisions in Saturn’s ring, the slate-coloured ring, and the inner satellites with great distinctness, likewise a and e Lyrae with their minute companions; and the superiority of this object-glass of 24-inches diameter in its command over the faintest points of light was admitted by all observers.
Equilibrated by a weight slung over a round brick tower, 64 feet high by 15 feet diameter, the tube could be placed at any altitude and at any azimuth by the observer himself - a railway carrying a light frame on wheels for its movement round the tower. The ease of manipulation was perfect, and the arrangements for neutralizing the vibration of this tube of 85 feet length produced the utmost steadiness. The late Mr. George Rennie (M. Inst. C.E.), who constructed the tube, declined to remove the blocks upon which it had been built save in the presence of Mr. Gravatt. The amount of flexure which took place, upon the removal of all but the end blocks, was, however, exactly what he had calculated it to be, and no more.
Both in the design and in the mechanical execution of this telescope, Mr. Gravatt proved himself not alone worthy of having sat at the feet of Troughton, but also in advance of the times. In more instances than one where he corrected the working formula of the leading authorities, the words of his friend Mr. Babbage were confirmed, when he said that - 'Gravatt’s mathematical capacity was of a high order, and mathematicians were glad to consult him ; when they had not done so, it was a great satisfaction to them to find that his opinion coincided with their own.'
The space-penetrating power of this giant refractor would have extended the boundaries of astronomic science ; but, in spite of Lord Spencer’s liberal gift of two acres on Wandsworth Common for it to stand upon, the unforeseen pecuniary difficulties of the person for whom it was constructed prevented its entire completion, and the whole is now falling to ruin; its tube, like a rejected toy, lying on the ground, 'Jacet ingens littore truncus avulsumque humeris caput et sine nomine corpus.' The only existing proof of its work is a photograph, about 9 inches diameter, of the full moon, taken by the Rev. J. B. Reade, on the principal focus, i.e., the focus of the object-glass, on the 6th of September, 1854, in which all the important features in the moon’s surface could be discerned. A positive print of this was sent to the International Exposition of Paris in 1855, and received ‘Honourable Mention,’ with a special notice in the Jurors’ Report.
When M. Scheutz, in 1854, brought his 'difference engine’ to London, Mr. Gravatt at once took up a subject which had long interested him, and he soon mastered the difficulties of that ingenious machine.
In 1855 he undertook the task of explaining to Prince Albert and to the Fellows of the Royal Society its principle and mode of action, and when it was placed in the International Exposition at Paris he continued to illustrate its construction and action ; in fact, 'Without him,' says Mr. Babbage, 'we should have had no calculating machine.'
The instrument, therefore, which was constructed by Messrs. Donkin after the Swedish original, and which is now worked at Somerset House under the direction of the Registrar-General, is due to Mr. Gravatt. Under his direction, specimens of logarithmic and other tables were calculated and printed without the use of types, thereby establishing the faith of the public in its capability of not only performing but also of registering complicated calculations.
He likewise calculated, stereoglyphed, and printed without the use of types, some mountain barometric tables, which, in the form of a brochure, were circulated among his friends.‘ Amongst the educated classes of the Chinese, who avoid politics, a taste for the mathematical sciences is very prevalent. The numerous translations of western scientific works attest this fact, and among their reproductions is the reprint by them of Gravatt’s “'Companion to the Mountain Barometer.' For his services rendered to science, in connection with the Swedish difference engine, he was elected Foreign Member of the Royal Academy of Sweden.
Mr. Gravatt joined the Institution of Civil Engineers as an Associate in 1826, and in 1828 he was transferred to the class of Members. He was a constant attendant at the meetings, frequently taking part in the discussions, especially on the occasion of novel, or abstruse questions. He took a prominent part in the discussion on the theory of the jet-propeller, and on the submerging of telegraphic cables.
It is always difficult to put, in an acceptable shape, before an assembly of practical men, a purely mathematical exposition of the fundamental dynamic conditions which underlie the solution of a practical problem; especially when, on the one hand, the elucidation involves intricate and abstract modes of thought, and when, on the other, the theoretical conclusions drawn therefrom must, in their application to practice, be largely modified by obvious, though collateral practical conditions. Now, Mr. Gravatt’s manner in discussion, though convincing in private, was not such in public as to master this difficulty so as to do justice to his matter.
It was perhaps attributable to these circumstances that, in the controversy which followed the reading of Mr. D. K. Clark's Paper in 1854 on 'Ruthven’s Propeller,' his view was warmly opposed by several eminent members of the Institution. Nevertheless, the view itself, exhibited in succinct and masterly mathematical language, is (regarded in a purely dynamical light, and taking account of its entire fundamental dynamic conditions) a true solution of the question at that time at issue. If by the labours of more recent investigators, like Dr. Rankine and Mr. Froude, this solution has, on the practical side, been extended, Mr. Gravatt’s, so far as it went, not only remains uncontroverted, but has received unqualified confirmation.
It is to be found among the pamphlets in the library of the Institution, in 'A Letter on Steam Gun-boats of shallow draught and high speed.'
His view of the mathematic-mechanics of laying submarine cables was clear and profound, and in himself wholly original; but not absolutely, with regard to others who preceded him in laying down the theory. At the termination of the controversy which took place between himself and the Astronomer-Royal, the latter said, 'Though I partly disagree, I do in great measure agree with you, and am rather surprised that with so little calculation you should have arrived at results of such general accuracy.'
Mr. Gravatt published in the 'Philosophical Magazine' of July, 1858, a further elucidation of the conclusions at which he arrived during the discussion on Messrs. Longridge and Brooks’ Paper read at the Institution in February, 1858.
Mr. Gravatt was, in the strictest sense, a remarkable man; peculiar to a degree which may fairly be called extraordinary, even in his defects, especially in those usually associated with want of sense, and implying that want; combined, however, with the possession on most points of the most solid and widely ranging perception and judgment - 'common sense,' in the strictest meaning of the term. He was like one of those wonderful pieces of work of his friend Troughton, which, for some small blemish or defect, its maker consigned to the limbo of the brass-box to be sold some day as old metal, although fit for all but the most perfect performance of the work for which it had been intended.
Capable of the warmest and most persistent friendship, Mr. Gravatt was also susceptible of strong resentment. This was, for the most part, based on a perception of wrong, as such, and expressed his strong and clear disapprobation of wrong doing.
It was also sometimes tinged with personal feelings, and warped by the operation of one or other of those disturbing mental forces which have already been alluded to; and, as a natural consequence, it was at such times often unjust. But if ever he came to see, as he was never unwilling to do, if proof came before him, that he had been induced into error, he was, in a manner unequivocally hearty, most forward to apologize. In fact, he was chivalrously honourable in all his feelings and transactions, and he never hesitated to admit that he had been in error.
The art of engineering men, such as the superior workmen at the Thames Tunnel, he possessed in an eminent degree, and had he been endowed with the same faculty, when he was brought into contact with men in general and with directors of public companies in particular, he would have attained success in life, in proportion to his capacity in engineering matters.
Of all the gifts presented to Mr. Gravatt, a pair of calipers made by Troughton’s own hands, Bryan Donkin’s chronometer by Hardy, and a specimen of Babbage’s original difference engine, were those which he regarded with the sincerest pleasure. These tokens consoled him when, finding himself passed in the race of life by men who did not possess his qualifications, he was led to the inference that they did so, not because they were sounder mechanics than he, but because they were more men of the world.
It would be very difficult to discuss, in a form suitable for the succinct Memoirs of the Institution, even a portion of the works upon which Mr. Gravatt was engaged. They were remarkable, not for their number, or for their magnitude, in the ordinary sense of that term, but for the amount of refined professional skill; and, if the word may be used, for the 'affectionate' scientific elaboration which they embodied. Some of the boldest and best contrived of his works, the great telescope, and the bridge over the River Parret, near Bridgewater, for instance, have not, in fact, survived.
The best memorial of his broad and deep professional knowledge, his varied acquirements, his versatile and kindly humour, would be a record of his table-talk, especially of such portions of it as belonged to the occasions when, in the company of various congenial friends, who, he felt, could appreciate and follow the current of his ideas, he gave full play to his mind. But of this the only record which exists is that which survives in the recollections of his friends. And such recollections, however intimate the friendship and congenial the temper of those who are their depositaries, are at best but ineffective substitutes for the portraiture which short-hand notes alone could adequately supply.
It would perhaps seem disproportionate, and perhaps unwarranted to say, that but for Plato the wisdom of Socrates would have been lost. Certainly, but for the indefatigable and almost unexampled labours of Boswell, we should scarcely have half known Johnson. And there undoubtedly have been men of great capacity and varied acquirements, who have possessed, besides great power of communicating their ideas in familiar conversation, whose gifts and whose accomplishments, though they have exerted a wide and deep influence on the current of contemporary thought, have yet left few permanent marks associated with their name and with their history, - 'carent quia vate sacro.'
Mr. Gravatt undoubtedly was one of these; and though many Engineers of the present day recollect, with more or less distinctness, how largely their stores of professional knowledge have been stocked from his warehouse; how greatly their forms of thought and methods of investigation have been influenced by his views, they could but poorly convey to others an inheritance which they feel to have been of life-long value to themselves.
The career of Mr. Gravatt was brought to an untimely end at Westminster, on the 30th May, 1866, under very painful circumstances. He was 'poisoned by an overdose of morphia given inadvertently by his nurse,' - a faithful and attached servant, to whom, in the jury’s opinion, 'sufficient caution was not given by the medical man in attendance.'
There was in Mr. Gravatt all the material to make an engineer; he possessed great acquirements, succeeded in almost everything that he undertook, wag full of high, chivalrous and honourable feelings, he had a kind heart and generous mind; and he ought to have taken a very high position in his profession; but in this he failed because he could not, or would not, conform to the ordinary ways of the men among whom his lot was cast.
1866 Obituary [2]
DEATH OF MR W. GRAVATT, C.E.
WE announce with unmixed regret, the decease of Mr. W. Gravatt, C. E., the well-known inventor of the "Dumpy" level, under peculiarly painful circumstances at the comparatively early age of fifty-nine.
Mr. Gravatt had been ill for about ten months, during which time he was attended by Mr Lee. Mr. Lee himself fell sick, however, and Dr. Poole was called in on the afternoon of Tuesday week. Dr. Poole wrote a prescription for a draught containing a large quantity of morphia. This draught was to be given in two doses, but, by a most unfortunate mistake, the nurse in attendance gave the whole at once. Mr. Gravatt never awoke in this world from the sleep which ensued. He passed away quietly and peacefully on the following morning.
Under the circumstances it became necessary to hold an inquest, which resulted in a verdict equivalent to one of accidental death.
William Gravatt, son of Colonel Gravatt, of the Royal Engineers, was early destined for the profession of a civil engineer, and after receiving an enlarged scientific education from his father, and being, it is believed, partly brought up at the Royal Military Academy at Woolwich, he went through a course of instruction in practical mechanics at the factory of Messrs. Bryan Donkin and Co.
He was then, towards the close of 1826, appointed one of the assistants at the works of the Thames Tunnel, and frequently remained all night in the frames, and more than once was known to have been there for thirty eight hours consecutively. It was in this year that he joined the Institution of Civil Engineers, of which he became a full member in 1828.
After the completion of the Thames Tunnel he was associated with the younger Brunel for many years on the Great Western Railway, and also on the Bristol and Exeter line, since which he had not been engaged in very active practice. He possessed high mathematical attainments, had a great attachment for astronomical pursuits, and was generally considered to be in all respects a very intelligent man. He was elected a fellow of the Royal Society in 1832, and of the Royal Astronomical Society in 1843, and he was also a foreign member of the Royal Academy of Sweden.
He took a very warm interest in Scheutz's calculating machine, which he first saw at Messrs. Donkin's factory in 1854, and which he subsequently explained to the scientific world at the apartments of the Royal Society at Somerset House, at the Paris Exhibition of 1855, and at the Institution of Civil Engineers.
An abstract of his method of considering and of working this machine appeared in a pamphlet issued by the Messrs. Scheutz ; and Mr. Gravatt himself had printed, by machinery, without the aid of types, for private circulation, in 1859, a "Companion to the Barometer," being " Mountain Barometer Tables," calculated and stereoglyphed by the second of Messrs. Scheutz's calculating machines, which machine was made by the Messrs. Donkin for the British Government., for the office of the Registrar General.