52 SELECTION AND USE 



price, and tlie stands which embody these improvements and 

 modifications are so distinct that they form a class by them- 

 selves, which may be designated the " New American Model.'' 

 None of the individual features found in this model aie new, 

 the most important of them having been embodied many years 

 ago in the English patent of Grubb, while others were used long 

 ago by Spencer in this country. But Grubb 's invention, so far 

 as we know, never came into use, and it was not until the year 

 1875, that the importance of the improvements in question be- 

 came generally recognized. Towards the close of that year, and 

 the beginning of 187G, four of the prominent microscope makers 

 of this country, viz., Bulloch, Gundlach, Tolles, and Zentmayer 

 seem to have turned their attention to the subject, and shortly 

 after brought out models on the new plan, the distinctive fea- 

 tures of which are the swinging of the mirror around a centre 

 which lies in the plane of the object ; the combination of a 

 swinging with a longitudinal movement in the slab-stage, and 

 the use of a very thin stage. Prior to this time, in all the best 

 microscopes of English and American make (at least as de- 

 scribed in the catalogues of the dealers), the sub-stage was made 

 to move only in the line of the optic axis of the instrument ; 

 the American makers took a new departure, and the new model 

 is the result. In its popular forms this model is characterized 

 by great simplicity in its working parts, while at the same time, 

 being provided with the very best means for adjusting and 

 registering the illumination, it is a stand which is sufficient for 

 the highest class of work, except, of course, in a few special 

 departments. 



So far as our knowledge goes there are at present before the 

 public four stands of comparatively low price, which may be 

 relegated to this class They are : The "Acme " of J. W. Sidle 

 & Co. ; the " Biological'' of Bulloch ; the " Histological " of 

 Zentmayer, and the "Investigator" of the Bausch & Lonib 

 Optical Company. The large stands of the Bausch & Lornb 

 Optical Co., of Beck, Bulloch, Boss, Tolles, Zentmayer, and 

 others, are of course quite as efficient as the small stands we 

 he.ye named, but the price is greater, and the convenience of 

 the small stands, when used as working microscopes, is in their 

 favor. At the end of this volume the reader will find plates 



