ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 



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semicircular guide until it finally rests in a horizontal position upon the 

 support at the end of the table. In this position the apparatus is at a 

 height of about 70 cm. 



Griffith's Photomicrographic Camera. — Mr, E. H. Griffith suggests 

 the use of a camera made of a wire spring cone in the place of the ordi- 

 nary bellows (fig. 176). 



The wire is properly tempered Fig. 176. 



and of sufficient diameter to keep 

 it in position. It is covered with 

 black tape to prevent reflection, 

 and a closely fitting piece of 

 black cloth or other suitable 

 material is placed over the entire 

 frame. For transportation the 

 camera may be put in a very small 

 space, and it is less liable to accident than those with bellows made of 

 leather. 



Jeserich's Focusing Arrangement.* — Figs. 177 and 178 represent 

 Dr. P. Jeserich's contrivance for working the micrometer screw from a 

 distance where the upper part of the 

 Microscope with the stage is made to 

 revolve, as in the Hartnack model, the 

 mechanism following all the changes 

 of position and the micrometer screw 

 not being loaded. S is a horizontal 

 endless screw working in bearings at 

 X X attached to the cross-piece of the 

 Microscope; at one end this screw 

 carries a grooved wheel R ox about 

 5-6 cm. diameter, which serves as a 

 pulley, any motion of which is com- 

 municated by means of S to the toothed 

 wheel Z, which is attached to the 

 micrometer screw. The endless cord 

 passes from R over two freely-moving 

 pulleys upon one axle attached by a 

 clamp to the face of the camera, and from these over two similar 

 pulleys at the other end of the camera ; beyond these a weighted pulley G 

 (5-10 grams) is suspended on the cord so as to keep it always taut. The 



Fig. 177. 



Fig. 178. 



least movement of the string is thus communicated to the micrometer 

 screw, while the whole apparatus is able to follow any movement of the 



* Jeserich, P., ' Die Mikrophotographie,' 8vo, Berlin, 1888, pp. 132-4 (3 figs.). 



