108 Microscopical Essays. 



D is a 'nut fitted to the faid fcrew, which, when turned, will 

 either feparate or bring together the two arms A C. 



E is a ft eel fpring, that feparates the two fides when the nut 

 is unfcrewed. 



F, a piece of brafs turning round in a focket, whence proceeds 

 a fpringing tube, moving on a rivet, through which runs a fteel 

 wire, one end of which finifhes in a point G, and the other end 

 hath a pair of pliers H foldered to it ; thefe are either to thruft 

 into, or to take up and hold any object, and may be turned 

 round as required. 



I, a ring of brafs, with a female fcrew fixed on an upright 

 piece of the fame metal, which turns on a rivet, that it may be 

 fet at a due diftance when the leaft magnifiers are ufed, and 

 ferves the fcrews of all the magnifiers. 



K, a concave fpeculum of filver, polifhed as bright as poffible, 

 in the center of which a double convex lens is placed, with a 

 proper aperture to look through it. On the back of this fpecu- 

 lum a male fcrew L is made to fit the brafs ring I, which may be 

 fcrewed into the faid ring at pleafure. 



Four of thefe concave fpecula, of different depths, are fitted to 

 four glaffes of different magnifying powers, to be ufed as the ob- 

 jects to be examined may require. The greater! magnifiers have 

 the leaft apertures. 



