THE MICROSCOPE. 



25 



Fig. 18. 



Dr. Withering, represented by fig. 18, which even now is 

 manufactured for sale ; it consists of 

 three brass plates, a b c, parallel with 

 each other, to the upper and lower 

 of which three stout wires, d e f, are 

 rivetted; the middle plate, b, forming 

 the stage, is made to slide up and 

 down on these three wires. The upper 

 plate, a, carries the lens, i, the lower 

 one, c, the mirror. Into the stage a 

 dissecting knife, h, a pointed instrument, 

 f, and a pair of forceps, g, are made to 

 fit, and can be readily taken out for 

 use by sliding the stage down nearly to 

 the mirror; this instrument was recommened by Dr. Withering, 

 and was first described in his Botanical Arrangements, its chief 

 merit being its simplicity. 



The compound microscopes described by Adams, are merely 

 modifications of that of his father, of Culpeper, of Cuff, and 

 of Benjamin Martin. The first, or that of the elder Adams, 

 was improved by the addition of a rack and pinion movement, 

 and by having aU the lenses set in a brass slider, so that they 

 may be placed one after the other under the compound body. 

 The second, or that of Culpeper, was made of brass, and was 

 improved in its optical part. Cuff's compound instrument 

 was much the same as that described at page 22 ; whilst that 

 of Benjamin Martin was improved by Adams himself, and 

 was made capable of receiving a single lens as well as a com- 

 pound body, and was furnished with a cradle joint, by which 

 the compound body could be inclined at any angle; the mirror 

 was double, both plane and concave; the legs, for convenience 

 of package, were made to slide one within the other. With 

 the work of Adams, in 1787, we may close our history of the 

 single and compound microscopes in their unachromatised 

 state, the discoveries at this time were few and comparatively 

 unimportant, and little or nothing more was exhibited by them 

 than the objects contained in the ivory sliders, with which all 

 the above described microscopes were supplied ; and he who 



