INVERTEBRATA, CRYPTOaAMIA, MICROSCOPY, ETC. 



145 



ring G, in which thirty objects are placed, the ring being rotated by 

 means of catches fixed to its outer margin, and each object can thus 

 be brought successively into the field of view. 



Fig. 10 



The Microscope tube D can be focussed by the ordinary rack and 

 pinion movement, and also (for fine adjustment) by the milled head F. 

 It is moved in two rectangular directions by other milled heads, E E, so 

 as to adjust the object in the field. A lamp H can be used if desired. 



New Binocular Microscope and Achromatic Objectives. — A 



preliminary announcement has been made of a binocular Microscope 

 " which is entirely new and original in its application of optical 

 principles as well as in its mechanical construction, and entirely over- 

 comes the difiicultics and defects of the Wenham plan." Also a 

 " globe lens," made on a " newly discovered optical principle, which 

 enables the highest corrections to be obtained by an adaptation of 

 the relative thicknesses only of the materials used." 



Steinheil's " Aplanatische Loupen." — These achromatic triplet 

 lenses arc constructed so as to be used at ar greater focal distance 

 from the object than most of the existing high-power lenses. They 

 are " Aplanatic," as their name implies, and it is claimed that they 

 give excellent definition over the whole field, even to such an extent 

 that they may be tilted to almost any angle without distortion, so 

 that the highest powers may bo readily used. The different focal 

 lengths of the lenses mounted for the pocket are 1^, ly',v, \l, ^ and §, 

 magnifying from 5.V to 2-i times. 



They can bo fitted in bronzed brass cupped mounts with holder, 

 for dissecting purposes, with magnifying powers from 3A to 21. 



Improved Illuminator for Diatoms and other Test Objects.*— 

 Mr. Wcnliam describes this contrivance as simple, easy to construct, 

 * ' English Mechanic,' xxx. (1879) p. 279. 

 VOL. III. L 



