ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 633 



MICROSCOPY. 



A. Instruments, Accessories, etc.* 

 CD Stands. 



Old Microscope by George Adams. — This Microscope was pre- 

 sented by Members of the Council to the Society's collection, and was 

 exhibited at the Meeting on June 16. 



The instrument, which is in excellent condition, almost as good as 

 new, has the following inscription engraved on it : — " Invented & Made 

 by Ceo. Adams at Tycho Brahe's Head in Fleet Street, London." It is 

 a combination of his " Xew Universal Single " and " New Universal 

 Double " Microscopes, described and figured in his " Micrographia 

 Illustrata," published in 1746. t 



It is not easy to assign a date to the instrument in the absence of 

 any description or reference, but as the same descriptions and figures 

 just referred to appear in the 4th edition of " Micrographia Illustrata " 

 published in 1771, it may fairly be concluded that the instrument now 

 described may be of a somewhat later date. 



Fig. 96 represents the instrument arranged as a Double Micro- 

 scope, and it is to a scale of about one-half the actual size. It 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 " scollop'd plate " as Adams terms it, 

 containing eight bi-couvex lenses of graduated powers, Xo. 1 being the 

 highest. The disk can be rotated beneath a fixed wheel, so that any 

 lens can be brought into use. The flat rim of the wheel protects the 

 lenses from dust, the arrangement thus clearly anticipating by about 

 130 years the principle of the modern dust-proof rotating nose-piece. 

 It is upon this flat rim that the inscription referred to is engraved. An 

 " eye " is formed in the periphery of the wheel, into which is screwed 

 the ornamental body, which is simply a glorified eye-piece, made of 

 ivory blackened and polished. 



When it is desired to use the instrument as a " Single Microscope " 

 the body is removed, and an eye-guard, very much like a lieberkuhn 

 inverted, made of blackened ivory, is screwed in in its place in order to 

 screen the eye from extraneous rays of light. 



The coarse-adjustment is effected by releasing the pinching-screw 

 at the back of the pillar, and raising or lowering the stem carrying the 

 disk and body to the required position, which is shown by index num- 

 bers on the octagonal pillar ; the screw is then tightened up, and an 

 object mounted in a " slider " placed on the stage will be in focus. The 



* This sub-division contains (1) Stands ; (2) Eye-pieces and Objectives ; (3) 

 Illuminating and other Apparatus ; (4) Photomicrography ; (5) Microscopical 

 Optics and Manipulation ; (6) Miscellaneous. 



t See also Mayall's Lectures on " The Microscope," delivered before the 

 Society of Arts in iS85, published in Journ. Soc. Arts, 1886. 



