204 SUMMARY OF CURRENT RESEARCHES RELATING TO 
and nut. This is really a throw-back to an older type ; for J. Marshall's 
(1704) Microscope possessed an inclinable limb carrying both body and 
stage, and was therefore far in advance of the telescope mount. 
The important point about this Microscope is the adaptation of a 
mirror, which now appears for the first time ; it also has a mechanical 
stage. 
1718. Fig. 33 shows Joblot’s simple Microscope. The ornamented 
plate carries the lens, the focus being adjusted by the nut and screw ; the 
plate next the ornamental one is a concentric rotary stage. The mechani- 
cal details of this stage are well thought-out and properly sprung (fig. 34). 
The instrument is a decided advance on any preceding simple Micro- 
Fig. 34. 
Fig. 35. 
scopes, not only on account of the mechanical contrivance of the concen- 
tric rotating stage, but also for an optical one, viz. the placing of a 
diaphragm at the end of the tube. 
Prof. Joblot also designed compound Microscopes ; these, although 
their exteriors are ornate and of good artistic design, are of a very crude 
type ; they possess, however, a concave lens in the covering cap of the 
eye-piece. This, when mounted in place of the convex eye-lenses, turned 
the instrument into what is now called a Briicke lens. 
1736. Barker’s catoptric Microscope, exactly like a Gregorian tele- 
scope, but of bad design. 
1738. Smith’s catoptric (fig. 35), very efficient of its class. It is 
