ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



251 



Winkel's Dissecting Microscope.* — This instrument (fig. 33) gives 

 greater working surface than most dissecting Microscopes. As will be 

 seen from the illustration, it has rack-and-pinion focusing adjustment 

 and also a rack-and-pinion movement for adjusting the optical system 

 in a horizontal plane, which, together with a rotary movement in the 



Fig. 33. 



same plane, permits of its use over any desired portion of the stage. 

 The arm carrying the optical system is slotted to receive either the 

 Porro erector, which can be used with ordinary objectives and eye- 

 pieces, or a ring to carry single lenses, both of which are provided, 

 together with silvered and opal reflectors for illuminating transparent 

 objects, and a plate with black and white surfaces — shown in the illustra- 

 tion swung aside — as a contrast background for opaque objects. 



* B. Winkel, Gottingen Catalogue, 1911, p. 50. 



