ZOOLOGY AND BOTANV, .MICKOSCOPY. ETC. 



739 



Lamps for alternating currents may also be adapted. The lamp is 

 provided with a rheostat for 110 volts. The two screws ^j a serve to 

 direct the crater accurately into the optic axis of the apparatus. The 

 screw b is for feeding the carbons. When the lamp is at the top of the 

 apparatus (fig. 121), the carbons may he regulated by a flexible rod affixed 

 at c. The position and working of the carbons may be watched through 

 the window/. For work in a lighted room, the apparatus is provided with 

 a cloth screen attached to a hinged ring of wood, which can be made to 

 envelop the condenser K, and secured by means of a screw h. When 

 the apparatus is required for projection, the locking arrangement E 



Fig 123. 



«hould be released, and B together with its optical equipment turned 

 al)Out the horizontal spindle R, until E fixes the optical axis in a 

 horizontal position (fig. 123). Photomicrographs are prepared with the 

 aid of a camera fitted with a dark slide available for plates up to 30 x 

 40 cm. The camera with the dark slide downwards should be placed 

 upon the drawing board and attached to the column S. After adjusting 

 the part B, the camera end should be moved upwards imtil the sleeve 

 at the camera end incloses the sleeve attached to the draw-tube of T, 

 or sleeve M when a microsummar is being used. This insures a light- 

 tight connexion between the two parts. For sharp focusing, the bellows 

 may be detached from the dark-slide holder (fig. 12-1). The imaare 

 Dec. 18th, 1907 3 C 



