ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



417 



C. Baker's Greenough Binocular Microscope. — This binocular 

 (tig. 53) is a combination of two Microscopes, unci, by the application of 

 Porro prisms, a convenient means of erecting the image and giving more 

 pronounced stereoscopic vision is provided. By rotating the prism-boxes 

 sufficient adjustment is obtained for varying the interpupillary distance 

 within normal limits. The tubes are arranged to bring the object into 

 focus at the same point in each field ; for this purpose they are set at 

 an angle to one another. The bodies are mounted on a slide having 

 rack-and -pinion movement, but no fine-adjustment is necessary on 

 account of the low magnification required of this class of Microscope. 

 The instrument can be inclined to 55°, and the hand-rests are so 

 arranged that they may be used w^hen the instrument is in either a 

 vertical position or at any inclination to this angle. The limb is attached. 



Fig. 54. 



by means of two thumb-screws, to a large square stage having a central 

 aperture fitted with a removable glass disk, and can be easily removed 

 and placed on the metal fork, as figured (fig. 54.) 



A universal size substage-tube, to carry a spot-lens for illuminating 

 the specimen on a darkground, is provided, and a mirror-box — contain- 

 ing concave mirror and matt-opal glass reflector, fitted on a swinging 

 arm — is mounted in gimbals. Three sets of specially paired objectives, 

 of 2j-in. 2-in., and Ij-in. focus, are made for this Microscope. The 

 magnification obtained by combining the objectives and eye-pieces ranges 

 between x 8*5 and x 52. 



C. Baker's New Model D.P.H. Microscope. — This instrument 

 (fig. 55) is provided with a body-tube U- in. in diam., in which sHdes 

 a draw-tube carrying an eye-piece 23*2 mm. in diam. ; it is fitted with 

 diagonal rack-and-pinion coarse-adjustment, which is carried on a Umb 

 cast in one piece, with an opening in which the fingers can be placed 

 when lifting. The milled-heads of the fine-adjustment are placed on 



