COMPARISON OF THE POWELL & LEALAND IMPROVED LARGE FIRST CLASS MICROSCOPE AND THEIR No 2

MAKER: POWELL & LEALAND

THE IMPROVED MICROSCOPE OF 1854 vs THE LATER No 2.:
These images allow for a comparison between the Powell & Lealand improved Large First Class Microscope dated 1854, and an example dated 1862 of the later Powell & Lealand No 2 stand into which it evolved. By 1860 the firm had developed a successor to their first class microscope, from then on referred to as their No 1 model, but it was decided to keep producing the original improved model alongside this as a slightly less elaborate option, with a few modifications, thereafter referred to as their No 2 microscope stand.

The most important changes included:
1.The stabilizing struts have been abandoned to allow for the use of an exchangeable binocular tube.
2.The cylindrical part of the limb accepting the bar with rack is longer (similar to the change from the 1843 to the No 3 models) 3.In later No 2 models, the coarse focus housing becomes hexagonal all the way to the top (see illustration from their 1871 catalogue).
4.The coarse focus knurled knobs are larger and now have a central locking screw.
5.In the fine adjustment mechanism,the nose-piece return spring is replaced by a helical coil acting directly upon it (the 2 small screw holes affixing the leaf springs are no longer present in the top surface of the arm).
6.The top stage plate configuration is different and now has an aperture to affix stage forceps.