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John Barton (1771-1834)
Later Sir John Barton.
1771 Born in Plymouth, 5 August.
1834 Died in Windsor, 25 August.
Sir John Barton served as deputy comptroller of the Royal Mint, and later as Treasurer to Queen Adelaide.
John Barton's wife was the granddaughter of John Harrison (1693-1776), of longitude fame. After his death, his wife Ann gave John Harrison's last pendulum clock to the Royal Astronomical Society.
He developed a micrometer, which he called the "Atometer" that was used for measuring small distances using a differential-screw technique, a Ruling Engine, and patented a method of creating metal ornaments engraved with parallel lines, using diffraction to create colours. An example of the latter are "Barton's Buttons", which were gold buttons stamped with a hard steel die on which Barton had cut hexagonal patterns.
1834 'THE LATE SIR JOHN BARTON
The following is an extract of a letter from Windsor, dated Oct. 21. :— "Our revered Sovereign, with that goodness of heart that characterizes all his actions, has commanded a mural tablet to be placed in the Cloister near the Deanery, to record the virtues of Sir John Barton. Monumental inscriptions are too frequently dedicated by ostentation or flattery; but this speaks the language of sober truth. Sir John was indeed from youth to age the affectionate and devoted servant of his Royal Master. All who had the advantage of knowing him will bear testimony to the excellence of his character. Kind and considerate to his inferiors; cheerful, friendly, and instructive in his intercourse with his equals; his inoffensive wit encouraged the timid and enlivened the dull. The persevering attention and inflexible integrity with which he discharged his official duties never for a moment degenerated into morseness or severity, for in him there was a rare and happy union of intellectual strength and constitutional cheerfulness. Well versed in astronomy, in metallurgy, in experimental and natural philosophy, he was often consulted by ingenious artists who sought to apply scientific principles to practical uses, and those studies which would have been labour to a frivolous mind were the delight and recreation of Sir John Barton. Frequently after a day of intense application to business has he devoted the night to the contemplation of heavenly bodies. The accuracy of his observations is well known to those scientific men in various parts of Europe with whom at different periods he corresponded. It may be sufficient to mention the names of Banks, Wollaston, Leslie, Cuvier, &c. &c. At the time of his death Sir John was deeply engaged in maturing a scheme for producing the parabolic curve in the lathes for the purpose of turning specula for reflecting telescopes, and it is very much to be regretted that he was not spared to complete a thing of so much importance to astronomy. Thus, equally qualified by his superior attainments to converse with a Herschell, to direct the construction of a mathematical instrument, or to detect the errors of machinery on a minute or on a stupendous scale, even his amusements tended to utility: But we must not omit to state in this faint tribute to his worth that neither the lofty pursuits of science nor his grateful attention to the interest of his illustrious patrons could weaken his faith as a Christian, or alienate his heart from the dear and honoured ties or conjugal and paternal affection. In every relation of life his conduct was exemplary, and he has left to his sorrowing family the rich inheritance of an unsullied name, and the invaluable example of a Christian death. On the 17th of June, 1834, the Duke of Saxe Meinengen, the brother of our Gracious Queen Adelaide, presented Mr. Barton with the Comthur Cross of the house of Saxe Meinengen, in approbation of his faithful service as her Majesty's treasurer, and the same day his Majesty King William IV conferred the honour of Knighthood upon him at Windsor Castle." '
Precision Engineering: Measuring, Engraving, etc.
The above information is condensed from Wikipedia.
Valuable information on an aspect of Barton's precision engineering work was published in 1947  from which the following information is extracted.
1806 He invented a measuring instrument using a differential screw, with which he stated that he could measure to 0.00001".
1822 Barton was granted a patent (No. 4678) for his beautifully engraved buttons. The Science Museum has a case of six of these, significantly classified under diffraction gratings. The machine (ruling engine) used to engrave the fine lines on the buttons, and was later used for engraving fine graduations and diffraction gratings. It came into the Science Museum's possession in 1925.
Precision Engineering: Screws
R. C. Brooks has provided valuable information on aspects of Barton's work. The following information is taken from that source.
R. C. Brooks includes a sketch of Barton's 'Atometer' (micrometer). It shows a screw of relatively large diameter, half of its length being threaded at 100 tpi, the other half at 110 tpi. Each half of the screw moves a jaw, shaped like those used on sliding calipers. The screw is rotated by a graduated wormwheel having 1000 teeth. The threads of the screw were said to have been cut using a diamond-tipped tool.
John Barton was a friend of Henry Maudslay, and shared an interest in producing screws of very accurate pitch. In about 1810 both men made a precision screw and submitted it to Edward Troughton for inspection. He found many minute irregularities, which spurred Barton and Maudslay to independently set about correcting the errors. Barton's method was to use two dies - separate but connected by links - and run back and forth to correct minute errors. Its claimed accuracy was such that, when engraving a diffraction grating with 2000 lines per inch, if a line was missed Barton could return the graving tool to the correct position and cut the line.
Regarding the Ruling Engine used by Barton, Brooks notes that it was stated in the Edinburgh Philosophical Journal in 1822 that it was made by William Harrison, the son of John Harrison, whereas the Science Museum considered it was more likely made by or with the assistance of Henry Maudslay. Some time after Barton's death the machine was sent to his grandson, Robert Barton, at the Melbourne Mint, before being donated to the Science Museum in 1925.