ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



659 



in the centre of the base of a " Baker's Laboratory Dissecting Micro- 

 scope " for giving the requisite support to the hands in dissecting on 

 the stage. An ordinary monocular body can be readily substituted 

 for the binocular when desired. 



Verick's Dissecting Microscope. — This instrument (Fig. 143) 

 does not differ in a sufficiently marked manner from the usual fonn 

 (though we have foimd it to be extremely conveniently arranged) to 

 require it to be noticed here, but a special advantage to which we 

 think attention may be usefully drawn is the mounting of the lenses, 

 which are fixed in a tubular setting of more than ordinary depth and 



Fig. 143. 



expanded at the top to receive the eye — similar, in fact, to a watch- 

 maker's glass. We are not able to say whether this additional depth 

 would in prolonged examinations develope any disadvantages ; but so 

 far as we have had the opportunity of judging, it constitutes a speci- 

 ally effective protection to the eye from extraneous light beyond what 

 is obtained in the case of the more ordinary setting. 



Gundlach's "Periscopic" Eye-pieces. — We have been asked for 

 a description of these eye-pieces, one of which was shown at a recent 

 meeting of the Society. The following description is by Mr. Guud- 

 lach himself: * — 



" The Huyghenian eye-piece in its original construction consists, 

 as is well known, of two plano-convex lenses, of which one, the ' field- 

 lens,' has three times the focal length of the other, the ' eye-lens ' — 

 the distance between the two being equal to double the focal length 

 of the eye-lens, the plane side of the field-lens facing the convex side 

 of the eye-lens. 



" The field-lens not only widens the field of view, but also corrects 

 the spherical as well as the chromatic aberration, as it is placed 

 beyond the focal distance of the eye-lens (the actual eye-piece), and 

 in consequence thereof acts negatively to the same. 



* Appended to a Catalogue of Microscopes. 



