ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 745' 



The slow motion has a double-speed lever action patent slow motion 

 invented by Mr. Ashe. The whole instrument is very massive, the 

 spread of the tripod being 8£ inches by I) inches, the height of the optic- 

 axis il^ inches, the maximum distance from the nose-piece to the stage 

 6 inches. 



A powerful clamp is supplied to the joint, and a square hole in the 

 limb of the Microscope allows illuminating apparatus to be carried on 

 the Microscope itself. 



R. & J. Beck's Metallurgical Microscope, " London Model." — This 

 metallurgical Microscope (fig. 1(3(J) is on the model of the "London" 

 Microscope, except that it is carried on a much larger pillar and base. 

 The latter, which is unusually large and steady, measures 6f in. in length 

 by 4J in. in width. 



The coarse focusing adjustment is by spiral rack-and-pinion, so 

 accurately fitted that even comparatively high powers can be focused 

 thereby. The fine adjustment consists of a triangular prism upon which 

 slides smoothly a solid metal sleeve which fits this prism so perfectly 

 that there is no lateral motion. The adjustment is obtained by a fine 

 micrometer screw actuating a supplementary pointed rod which impinges 

 upon a hardened steel block. The limb of the Microscope is so designed 

 that there is ample room for the fingers when turning the milled 

 heads. 



The body is made of a large diameter, 1'27 in., No. 3 Royal Micro- 

 scopical Society's standard gauge, so that a large angle of view can be 

 obtained for photo-micrography, or large field eye-pieces can be used if 

 desired. 



The stage is carried on an exceedingly strong dovetailed slide, and 

 has a rack-and-pinion focusing motion up and down of 2 in. 



The mechanical stage gives vertical and lateral motion of 1 in. and 

 is very solidly constructed. If the mechanical stage is not supplied, a 

 square stage, 3f in. by 3J in. of solid construction is supplied. 



A substage with screw-focusing adjustments is supplied in the most 

 complete form, but the instrument may be supplied with or without 

 this adjustment. A double mirror and strong case accompany each 

 instrument. 



Ashe-Finlayson Comparascope. — By the use of this apparatus 

 (rig. 167), exhibited at the October Meeting, exact comparisons may be 

 made of two objects which may be seen side by side in the same field of 

 view. For certain classes of microscopical work this is most valuable. 

 It is applied without any difficulty to any ordinary monocular Micro- 

 scope, as the apparatus may be screwed in like an object-glass and be 

 clamped at any convenient position so that it projects at right angles to 

 the body of the instrument, either in the front or to one side or the 

 other, according to the most convenient position from which to take 

 the light. 



The whole apparatus, by means of an adapter A, fig. 168, screws 

 into the body of the Microscope in place of the object-glass, and the 

 ordinary object-glass screws into the apparatus as shown at 1. 



