Henry J Grayson (1856–1918) with his micro-ruling engine
William Stone (b.1858, d.1949)
Henry Joseph Grayson was trained as a gardener and had a keen interest in microscopy for botanical studies. At the time, microscopes were calibrated using rulings - slides with evenly spaced lines of known pitch (picth is the distance from the centre of one line to the centre of the next). But the available rulings were not adequate for accurate measurements, prompting Grayson to construct a new type of machine to produce precision rulings.
Grayson's first version of of a micro-ruling engine was made from wood and glass, and was capable of producing as many as 40,000 lines per inch. Their quality far exceeded any others available at the time. In the early 1900s Grayson became a member of the Faculty of Science at the University of Melbourne. Micro-ruling engines made by Grayson still exist and are held in the School of Physics and at the Medical History Museum.
This plate negative is the only known photographic image of H.J. Grayson with his micro-ruling engine, before minor modifications were made to the vernier wheel. Three photographs made from the negative were created.
The plate negative was discovered at the same time as the micro-ruling engine.
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12.6 x 17.3 cm, 19.2 x 19.7 cm and 43.6 x 55.3 cm (photographs)
name/inscriptions ▫ on label on image: 'The only known photograph of Henry/Grayson. It shows the ruling machine/before minor modifications to the/vernier wheel.' ▫ .5
name/inscriptions ▫ verso: 'THIS IS THE ONLY KNOWN PHOTOGRAPH OF/GRAYSON. IT WAS TAKEN BY WILLIAM STONE/AND THE PLATE NEGATIVE FOUND WHEN THE/MICRORULING ENGINE WAS DISCOVERED. IT/SHOWS THE ENGINE BEFORE MINOR MODEIFICATIONS/WERE MADE TO THE VERNIER WHEEL.' ▫ .5