2JC> OPTICS. 



The following is a single microscope for opaque 

 objects, which remedies the inconvenience of hav- 

 ing the dark side of an object next the eye, which 

 has hitherto been a great obstruction in making 

 observations on opaque objects. 



The several parts of this instrument, commonly 

 made of brass, are as follow : 



Through the first side A passes a fine screw B, 

 the other end whereof is fastened to the moveable 

 side C (Fig. 2.) 



D is a nut adapted to the said screw, by the 

 turning of which the two sides A, C, are gradually 

 brought together. 



E is a spring of steel, that separates the said two 

 sides when the nut is unscrewed. 



F, a piece of brass turning round in a socket, 

 whence proceeds a small spring tube, moving upon 

 a rivet ; through this tube there runs a steel wire, 

 one end whereof terminates in a sharp point G, 

 and the other has a pair of pliers, H, fastened to 

 it. The point and pliers are to thrust into, or to 

 take up and hold any insect or object : and either 

 of them may be turned upwards, as suits the pur- 

 pose best. 



I is a ring of brass with a female screw within 

 it, mounted on an upright piece of the same metal, 

 which turns round on a rivet, that it may be set at 

 a due distance when the least magnifiers are em- 

 ployed. This ring receives the screws of all the 

 magnifiers. 



P, a nan die turned of wood, to screw into the 

 instrument when it is used. 



K, a concave speculum of silver, polished as 

 bright as possible, in the centre of which a double 

 convex lens is placed, with a proper aperture to 



