ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



497 



the ordinary Microscope form, so that in addition to the rack-and-pinion 

 adjustment there is also a fine-adjustment by prism action and micrometer- 

 screw ; in consequence, stronger magnifications can be used. The great 

 distance of the measuring stage from the pillar is notable, as well as the 

 provision of stage spring-carriers, so that plates of 16 cm. by 16 cm. can 

 be applied and their central parts measured. The details of the measuring 

 stage, the illumination, the measuring screw, and the reading scales, are 

 practically the same as for model II. The Microscope has one ocular 

 and three objectives, giving about 10-100 diameters ; stronger objectives 

 can be used if desired. The ocular has strong threads, and is rotatory 

 through 90°. 



Vogel's Measuring Microscope (Model IV.).* — This instrument 

 (fig. 127) is the oldest form of measuring instrument constructed by 



Fig. 127. 



Messrs. Toepfer und Sohn (catalogue number, 9c). The principle is 

 essentially that of a Microscope, with fine-adjustment and horse-shoe 

 shape, hinged pillar for inclination, and a glass plate as object-carrier. 

 The available part of the measuring screw extends to 30 mm, and the 

 pitch is 0*5 mm. The scales read to 0*0005 mm. by means of two 



* Otto Tospfer und Soma's Catalogue (Neue Astrophisikalische Appaiate, 

 (1808), Potsdam. 



Aug. 19th, 1908 



2 L 



