Microscopical Essays. 109 



M, a round object plate, one fide white, and the other black, 

 intended to render objects the more vifible, by placing them, if 

 black, upon the white, and if white, on the black fide. 



A fteel fpring N turns down on each fide, to make any object 

 fall : from the object plate there is a hollow pipe, to fcrew it on 

 the needle's point G. 



O, a fmall box of brafs, with a glafs on each fide, contrived 

 to confine any living object in order to examine it ; this alfo has 

 a pipe to fcrew upon the end-of the needle at G. 



P, a turned handle of ivory, to fcrew into the inftrument when 

 it is made ufe of. 



Q, a pair of pliers to take up any object, or manage it with 

 conveniency. 



I 



R, a foft hair brufh, to clean the glaffes or fpecula. 



When you would view any object, fcrew the fpeculum, with 

 the magnifier you intend to ufe, into the brafs ring I ; place your 

 object either on the needle G, in the pliers H, on the object 

 plate M, or in the brafs hollow box O, as may be moft conve- - 

 nient, according to the nature and condition of it; then holding 

 up your inftrument by the handle P, look againft the light ' 

 through the magnifying lens, and by means of the nut D, toge- 

 ther with the motion of the needle, by managing it's lower end, 

 the object may be turned about, raifed or deprefied, brought 

 nearer the glafs, or put farther from it a till you hit the true focal 



diftance a 



