166 Transactions of the Society. 



7. C^dpeper's Microscope, improved by Scarlet (c. 1725). 



Tills tripod form of Microscope stand, mounted on a wooden 

 box, was a favourite model for more than a century. It was 

 copied and made by successive opticians with many variations in 

 form, material, and finish until about the middle of last century. 

 The body of the present model is made of wood and cardboard, 

 and the focusing is done by sliding the body. There is no fine- 

 adjustment. The object-glass is a single biconvex lens, and the 

 eye-piece has two lenses. A mirror with ball-and-socket motion 

 is fixed to the box foot. These makers placed a conical ivory 

 diaphragm below the stage to cut off part of the light under 

 certain conditions. 



This instrument is described in li. Smith's " Opticks " 

 (Cambridge, 1738), ii. p. 407, and figured in Mayall's Cantor 

 Lectures, 1885, p. 40. (See Journ. E.M.S., 1909, p. 654.) 



No improvement in the definition. 



8. Nathaniel Adams' Microscope (c. 1740). 



This is of the Culpeper and Scarlet pattern, and is rendered 

 even more unhandy by the addition of a fourth pillar in the space 

 surrounding the stage. This inconvenience was incurred, no 

 doubt, for the sake of the greater rigidity secured by the fourth 

 pillar — a distinct advantage in focusing the instrument. Atten- 

 tion may be drawn to the elaborate chain of ball-and-socket joints 

 by which a condensing lens is connected to the stage. (See 

 Journ. E.M.S., 1905, p. 397 ; and 1909, p. 654.) 



The concave mirror is fixed, and it is consequently very 

 difftcult to obtain satisfactory illumination. There is no change 

 in the definition. 



9. George Adams' "New Universal Single and Double 

 Microscope" (c. 1746). 



This Microscope has a folding tripod base, from which rises 

 an octagonal pillar, bored out to receive a cylindrical stem that 

 slides telescopically within it. The stem carries an eight-lobed 

 disk or "scalloped plate," as Adams terms it, containing eight 

 biconvex lenses of graduated powers. The disk can be rotated 

 beneath a fixed wheel so that any lens can be brought into use, 

 whilst all the others are protected from dust by the flat rim, 

 anticipating by 130 years the modern dust-proof, rotating nose- 

 piece. The body is made of blackened and polished ivory. The 

 coarse-adjustment is effected by releasing a pinching screw at the 



