ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



493 



urination of the object is attained by a rotatory long mirror placed 

 underneath the stage. The Microscope is on a rail parallel to the 

 measuring screw, and is adjustable by hand-movement, by which 

 the arangement of long objects — e.g. spectra — is much facilitated 

 Microscope is equipped with one ocular and three objectives, 

 about 4-100 diameters ; focusing is by rack-and-pinion. The ocular 

 has strong threads, and can be rotated through 90°. 



means 

 . The 

 giving 



Fig. 123. 



Vogel's Measuring Microscope (Model I.).* — This apparatus of 

 Otto Toepfer und Sohn (Xo. 9 in their catalogue) serves for almost the 

 same purpose as model C, but the Microscope is intended to be used in a 

 constant position. For this purpose the Microscope is movable by hand 

 on a slide, and is provided with a prism in order to be convenient for 

 the observer. The illumination of the measuring screw, its gradation, 

 and the optical equipment, are the same as in the similar parts of the 

 measuring stage of model C. As will be plainly seen from the illus- 

 tration (fig. 124), the apparatus may be accompanied with an etching 

 installation which can be adjusted and clamped on the slide of the 

 Microscope. This auxiliary gives a means of engraving fine divisions on 



* Otto Toepfer und Sohn's Catalogue (Neue Astrophvsikalische Apparate 

 1908), Potsdam. 



