SELLIGUE

SELLIGUE

Alexandre François Gilles dit Selligue (sometimes seen as Seligue) (1784-1845)

Except when absolutely necessary, Gilles used his “dit name” for his professional activities. He has been described as a mechanical engineer, an optician and a maker of mathematical instruments and as a mineralogist and instrument maker. He seems to have excelled at generating brilliant ideas and then persuading others to implement them, while giving his name to the final product (see the story of the microscope, below). He is credited with being the first to develop processes for extracting oil from shale, and for generating gas for lighting, among others, and held a number of mining concessions. He once tried to take a barometer that he had made up Mont Blanc to try it out, but had to turn back! Since the name “Selligue” is synthetic and does not appear in official registers (note that the first 6 letters are his surname, reversed), it seems that he was also the publisher of a number of books including the Journal du Commerce. His contribution to microscopy was also significant.

Selligue designed a high power achromatic objective by combining a series of relatively low power achromatic lenses. Each achromatic lens was itself made by combining a plano-concave flint glass lens with a bi-convex lens to get the achromatic effect. Such combinations were easier to make than a single lens of the same strength. The microscope was made in 1824 by Vincent (c. 1770-1841) and Charles (1804-1859) Chevalier, who bore the cost of the development and construction. It had four pairs of lenses, screwed together and apparently gave good results up to magnifications of 200×. However, each individual lens contributed to the overall spherical aberration of the lens. Chevalier managed to correct for this, somewhat, by adjusting the positions of the lenses. There is a microscope resulting from this partnership in Geneva.

Selligue presented the microscope to the French Academy of Sciences in 1824, with generally favourable results. Unfortunately, he did not mention the contributions of the Chevaliers and the partnership came to an acrimonious end. Selligue turned to Rochette Jeune for further production of his microscope. The Chevaliers went on to market their improved version with their own lable on it.