Adams's " Variable " Microscope. By Id yard M. Nelson. 179 



of all the ancient Microscopes, because in it we find embodied the 

 main principles of the Microscope as constructed at the present 

 time. It may briefly be described as a stand with a hinged joint at 

 the top, to which is attached a bar carrying the body, the stage, 

 and the illuminating apparatus, i.e. the mirror. If, therefore, the 

 Microscope body is inclined, the stage and the mirror are inclined 

 with it, precisely as in the Microscopes of to-day. 



The first Microscope to have a limb carrying the body, stage, 

 and mirror attached by a joint to a stand in this manner, is that of 

 F. Watkins * (1755), fig. 25, but there the idea was carried out 

 in such an impossible manner that even when it was merely 



Fig. 26.— Cufi, 1765. 



touched it could not help shaking like an aspen, for the pivot was 

 at the tail end of the limb ; but, be that as it may, it probably gave 

 the idea to the noble inventor of the " Variable," who in a thoroughly 

 practical manner corrected the faults of the Watkins Microscope. 

 Previous to Watkins's Microscope, there were tube or drum Micro- 

 scopes, and those on the telescope plan, where the object at which 

 the Microscope was pointed was disconnected from the body. 

 Hertel's Microscope, the first to possess a mirror (1715), was built 

 on this telescope plan. Bonami's Microscope (1691), the first to 

 have the object and illuminating apparatus connected to the body, 

 was a type by itself ; for the whole apparatus was fixed to a base- 



* Journ. R.M.S. 1908, p. 137. 



