ABSTRACT
The Exhibition is rich in its collection of microscopes of all kinds, comprising instruments varying from the simplest forms to the most elaborate. With a happy combination of mathematical knowledge and practical experience, Mr. Lister continued to pursue the subject, and in the year 1830 he published in the “Philosophical Transactions” his paper on ‘Aplanatic foci of the double achromatic object-glass, with other properties belonging to it. Ross and Powell had taken up the manufacture, but without much advance on the first simple application of the principle until the beginning of 1837, when, at the suggestion of Mr. Lister, Mr. Ross constructed a differently-arranged combination, but on the same basis. This combination was successfully worked out, and was designed to produce a great increase of defining power. Ladd exhibits a microscope furnished with chain and spindle movements, in place of rack and pinion.
