ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



207 



holding the mirror, so that the distance between the eye-piece prism and 

 the mirror can be regulated. Diaphragms of coloured glass are also 

 attached to the stem, and can be rotated into position, as required. 



Fig. 28. 



TJi^^ 



(4) [Photomicrography. 



Queen's Photomicrography of Metals.*— The camera arrangement 

 shown in fig. 29 has been designed by Msssrs. Queen, of Phila- 

 delphia, for the photomicrography of metals. The camera is so 

 hinged that it may be tilted aside for ocular examination of the object, 

 selection of spot to be photographed, adjustment of light, &c. ; then 

 replaced vertically and connected with the tube of the Microscope. The 

 source of light is a Welsbach gas-burner completely surrounded by a 

 metallic cylinder leaving only the necessary aperture for the illumination 

 of the object. The emergent pencil of light may be controlled by an 

 iris diaphragm fastened to the burner. The light is received by a con- 

 densing lens adjustable in height, and then by a vertical illuminator 

 screwed between the body of the Microscope and the objective. The 

 Zeiss model of vertical illuminator, consisting of a totally reflecting 



Metallographist, i. (1898) p. 167 (1 fig.). 



