DESCRIPTION OF DR. GORINCs BNGISCOPB. 



screw, the milled head of which, u, is seen in the draw- 

 ing. Above the wheel is shewn the triangular pinion 

 socket, v, which carries the arm, w, which is also of gun- 

 metal, truncated at its edges with a sunk rack on its 

 superior side, exactly on the principle of the other : this 

 bar is worked by a pinion, x t seen in the cross elevation 

 of this socket and bar, fig. 10. Diamond and sapphire 

 lenses, and all sorts of simple microscopes, are attached 

 to this arm, by being thrust into the hole at its other 

 extremity, as drawn in the engraving. 



The superiority of sapphire lenses over those of glass 

 seems now universally recognised, and virtually, the su- 

 periority of diamonds over sapphires. (For whatever will 

 prove the former of these propositions will most assuredly 

 prove the latter also.) If these substances possessed no 

 other advantages over glass, save their invulnerability 

 and capability of being burnished into their brass settings, 

 these properties, coupled with their extreme thinness, the 

 natural result of their shallow curves, when properly 

 executed, (and which allows more room for the object 

 and for the illumination of it, if opaque, with any given 

 power and aperture,) and their superior magnifying 

 power with a given curve, also would fully justify the 

 patronage they have received*. 



The pinion, #, fig. 10, has a projecting square at each 

 end, to receive the ivory milled lever, y, or milled head, 

 z, on either side. The whole of this socket revolves on 



* See Microscopic Cabinet, chap. xiv. 



