ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 115 



in the cloth-lined socket for the coarse adjustment, or rack and pinion 

 can be provided. 



The fine adjustment is shown above (Fig. 6). 



Sidle's New "Acme" Microscope.* — Messrs. John W. Sidle and 

 Co., of Lancaster, Pa., U.S., the manufacturers of the small " Acme " 

 stand described and figured at pp. 522-3 of vol. iii. (the result of the 

 combined suggestions of Professor J. E. Smith and Mr. Sidle), have 

 perfected a larger stand substantially on the same model. 



The binocular prism is contained in a sliding box, in a nose-piece 

 that fits in the lower end of the body-tube by a bayonet-joint. By 

 removing the nose-piece a clear field is given to lenses having the 

 l|-inch screw, and by screwing into this thread an ordinary adapter 

 with " Society " screw one is prepared for the use of low-power lenses 

 of large apertures. This is an improvement, as most of the binocular 

 stands do not permit of the employment of wide-angled objectives to 

 their best advantage, in consequence of the diaphragms usually applied 

 in the main tube. 



The substage swings on a circle of 3f inches diameter, and is gradu- 

 ated to degrees. It moves along the swinging-bar by rack and pinion. 

 The substage may be centered in the optic axis by two milled heads. 

 This centering arrangement is of new construction, and is contained in 

 the space between the substage ring and the slide, thus doing away 

 with the large ring and set-screws found on some substages. 



ToUes-Blackham Microscope. — We gave, in vol. iii. (1880) 

 p. 520, a brief description of this stand, illustrated by a figure. Since 

 that date an improved form has been constructed for Mr. Crisp, which 

 he exhibited at the Society's November meeting, and which we here 

 describe. The figure noted above should be referred to together with 

 those now given. 



Mr. ToUes has changed the shape of the foot ; it is now in the 

 form of an equilateral triangle, with concave sides and truncated 

 angles, having pads of cork under each end. On the centre of the 

 base a circular plate is . turned, and on this rotates a second plate, 

 carrying the pillars of the Microscope ; the upper plate is graduated 

 for measuring angles, and can be firmly clamped at any point. 



At the back of the vertical disk, a "radial arm," to carry a 

 mirror or other accessory is fitted to rotate laterally concentric with 

 the object. 



An extra large milled head slips on the upper part of the pinion 

 of the fine focussing screw, which is intended primarily for use in 

 focussing for micro-photography ; for this purpose it is grooved round 

 the edge, so that a thread may be wound on it and the focussing 

 controlled some distance off. For ordinary high-power work, this 

 large milled head adds to the sensitiveness of the focussing ; it has 

 been thus applied by Mr. Tolles for many years past. 



The draw-tube is nickel-plated, and is said not to become sullied 

 so readily by handling as the usual brass tube. It is graduated, and 



* Amer. Mon. Micr. Journ., i. (1880) pp. 203-4. 



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