ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 105 



isolated micrometer screw, whereby side movement is entirely eliminated. 

 The fitting carrying the body or optical tube is new and of a novel 

 construction, such that the wear and tear indispensable to all fittings 

 can be compensated for by means of a simple adjustment effected by 

 three screws fitted to the limb. The coarse adjustment is by means of 

 Swift's patented diagonal rack-and-pinion. The stage is larger than 

 that usually supplied to students' stands, and allows of the free use of 

 a Petri dish. The whole of the instrument, with exception of the tripod 

 and stage, is polished bright, and is of the highest possible mechanical 

 excellence. The -jUin. objective supplied has an exceptionally long 

 working distance for blood examination with the Thoma-Zeiss haema- 

 cytometer. 



Swift's Continental Stand.* — The makers have introduced this 

 stand (fig. 4) for the convenience of those who prefer this style. A 

 special plant of machinery has been put down for the manufacture, and 

 the instrument is an absolute replique of a stand manufactured by one 

 of the most reputed German makers, and is listed at the Continental 

 price. A variation is, however, introduced in the size of the stand, 

 which is much larger than in the original, and allows of the free use of 

 the largest Petri dishes. 



Watson and Sons' "Works" Metallurgical Microscope. f — The 

 form and construction of this instrument are shown in fig. 5, and 

 resemble the "Van Heurck" model made by the same firm. The foot 

 is of the tripod pattern, and its front is so shaped that access is freely 

 obtained to the milled heads, which control the movements of the stage 

 and substage. The spread is 9§ in. The instrument can be inclined 

 on the foot in any position from the horizontal to the vertical ; a 

 clamping screw being provided for fixing it firmly in position. The 

 stage is mounted on a very substantial bracket which, at the back, is 

 fitted by dove-tailed grooves into a frame in which, by rack-and-pinion, 

 it can be raised or lowered to or from the body of the Microscope. 

 Special attention has been given to affording a sufficient interval 

 between the nose-piece of the Microscope and the surface of the stage, 

 for the use of very low-power objectives. The coarse adjustment 

 afforded by the rack-and-pinion has, in many instances, been supple- 

 mented by a fine adjustment, so that the whole focussing of the speci- 

 men can be done from the stage instead of with the Microscope body. 

 The stage usually supplied is similar to that of Watson's " Circuit 

 Stage Van Heurck " Microscope with mechanical screws, having a range 

 of motion of one inch in each direction. Complete rotation is provided, 

 so that specimens may be examined under every aspect of illumination. 

 In the illustration it will be seen that a sliding bar is fitted to a recess in 

 the stage ; this bar may be instantly removed, and a levelling stage or 

 metal holder may interchange with it. The body is of extra large 

 diameter, and is fitted with two draw-tubes ; one having a rackwork, 

 and the Other sliding, so that a wide range of body-length may be 

 obtained. There is sufficient range of adjustment for the focussing of 

 the lowest-power lenses. The instrument is recommended by the makers 



* J. Swift & Son's special Catalogue, London. 



t W. Watson & Sons' Catalogue of Micro-outfits for Metallurgy, pp. 1, 3, 4. 



