Microscopes and Microscopical Accessories #266418

The apertures indicated are the guaranteed minimum values; the stated focal lengths are adhered to as closely as possible. Remarks on the use of the 2mm Apochromatic Lens of mm aperture (homogeneous immersion). Owing both to the hyper-hemispherical form of the front lens, which is held in situ by a very narrow ridge at the extreme edge of the setting, and its rela tively short working distance this lens demands careful treatment and should, in particular, he scrupulously guarded against shocks or pressure. As compared with the 2 lens of aperture this lens possesses a greater resolving and defining power in the proportion of 14: 13 and gives a brighter image in the proportion of 20: The 2 is a decided advantage where exceptionally intricate problems requiring the most delicate apparatus have to be solved, and also in such cases where the lens is to serve as a means of controlling observations made with lower powers; for regular work preference should be given, generally speaking, to the 2mm owing, to the greater firmness of the frontal lens.