Page:Dictionary of National Biography volume 33.djvu/353

 LISTER, JOSEPH JACKSON (1786–1869), discoverer of the principle upon which the modern microscope is constructed, born in London on 11 Jan. 1786, was son of John Lister of Stoke Newington, a wine merchant, and his wife, Mary Jackson. His parents were members of the Society of Friends. At fourteen years of age he left school to assist his father in the wine trade; but though for many years closely occupied in business, he contrived by early rising and otherwise to largely supplement the education he had received at school, and was as regards his mathematical knowledge a self-taught man.

His predilection for optics manifested itself early. When a child he enjoyed looking at the prospect through air-bubbles in the window-pane, which improved the vision of his then myopic eye, and enabled him to see distant objects with distinctness. This fact afterwards led him to think it probable that in very young children the eye is generally myopic. At school he alone of all the boys possessed a telescope.

The achromatic microscope was early an object of interest to him; but it was not till 1824, when he was thirty-eight years old, that he did anything to improve the object-glass. His first work of this kind is recorded in a note in the possession of the author of this memoir, dated 1825, to the following effect: ‘The 4/10 and 2/10 achromatic object-glasses, made by W. Tulley at Dr. Goring's suggestion, delighted me by their beautiful performance, but they appeared to me to have a great disadvantage in consequence of the thickness in proportion to their focal length, which W. T. thought could not be avoided. I therefore induced him to make for me one of 9/10, much thinner in proportion, and had the satisfaction to find its performance very nearly equal to his best 2/10. In one respect, indeed, it is superior; showing when in good adjustment the reflection from a minute ball of mercury a bright point in any part of the field, while in the 2/10 and 4/10 it is so shown only in a small portion of the field near the centre, and in the rest has a bur shooting outwards.’ This bur, of which a sketch is given, is the first mention of the ‘coma,’ which afterwards formed so important a subject of his investigations. The note goes on to describe a suggestion for another combination, illustrated by drawings of magnified views of the curves of the glasses, executed with his usual extreme neatness and accuracy; and it concludes with the words: ‘tried many experiments to ascertain the best means of correcting small errors in aberration.’ This note is the first of a long series of accounts of experiments, with remarks upon them. The notes are beautifully arranged, and are well fitted for publication.

In 1826 Lister gave Tulley further projections of object-glasses, and made a sketch for the engraver to illustrate a description of Tulley's microscope, which that optician published, with a fitting acknowledgment of his indebtedness to Lister's ingenuity and skill. Besides the improved object-glasses, Lister designed for this instrument a graduated lengthening tube to the body, the stage-fitting for clamping and rotating the object, a subsidiary stage, a dark well, a large disc, which would incline and rotate for opaque objects, a ground-glass moderator, a glass trough, a live-box made with flat plate, a combination of lenses to act as condenser under the object (apparently the first approach to the present achromatic condenser), the erecting-glass, and the adaptation of Wollaston's camera lucida to the eye-piece. The value of the erecting-glass for facilitating dissections under low powers is perhaps even yet not sufficiently appreciated. The camera lucida had long been a favourite instrument with Lister for drawing landscapes, and the tripod which he invented for supporting the drawing and the camera is that which is now universally used by photographers.

In December 1826 Lister's notes supply an account of an examination of a set of four plano-convex lenses, each consisting of a biconvex of plate-glass and a plano-concave of flint-glass cemented to it by varnish, constructed by Chevalier of Paris. Here Lister records for the first time some puzzling appearances in combinations of compound lenses, which ultimately led him to his great discovery of the two aplanatic foci. Each of Chevalier's compound plano-convex lenses when used singly presented a bur or coma outwards, but when two of them are combined this coma, instead of being exaggerated, as might have been expected, was ‘less than with any single glass,’ while the performance was in other respects satisfactory. ‘Observing the advantages resulting from this combination,’ Lister ‘tried some others,’ among the rest two of Tulley's triple glasses, each of which taken singly was of fine performance. But, instead of unmixed improvement resulting, he noted: ‘N.B. Each glass separately shows a bright object all over the field without bur, and is not far from being achromatic. But combined the objects not in the centre have a strong bur inwards, the colour is much under-corrected, and the spherical aberration is not right.’ 