482 



SUMMARY OF CURRENT EESEAJiCHES RELATING TO 



In ReicJierfs apparatus (fig. 135) the camera C slides on a base-board 

 between guides a and b, a graduated scale and index z recording the position. 

 It can be levelled by screws s at one end. The lengthening-piece Z is 

 removable when the camera is required to be brought nearer to the Micro- 



FiG. 134. 



scope. The ground glass is moved by rack and pinion T, or for fine- 

 adjustment by m. 



The Microscope D is connected with the camera by a light-proof con- 

 nection at K, and is fastened to the base by a screw at F. The fine-adjust- 

 ment screw head E is toothed, and is turned by a larger toothed wheel u 

 which is actuated by the prism g at the end of the rod S}). The other end 

 of the rod reaches to k wliere it is turned by the milled head h. 



For illumination by transmitted light a mirror P and condensing lens L 

 slide in the groove I. There is also a holder B for holding fluids, either 

 for controlling the illumination or for stopping the heat rays. For opaque 

 objects there is a second mirror H on a suj^port r. 



SeiherVs (fig. 136) and VericFs (fig. 137) have each special arrange- 

 ments for focusing. In the original form of the former the screw head had 

 teeth cut in it in which a toothed wheel worked, the wheel being actuated 

 by a double-jointed rod. This is now modified, as shown m the fig., a 

 system of pulleys and cords being used. In the latter there is a rod and 

 one pulley, the head of the fine-adjustment screw being also grooved to 

 receive the cord. 



For photomicrography Dr. Zeiss modifies his No. 1 stand as shown in 

 fig. 138. The chief difierences are that the body is shorter and of greater 

 diameter, so as to interfere as little as possible with the cone of rays trans- 

 mitted by the objective, and that there is an extra large (140 x 120 mm.) 

 mechanical stage with circular and rectangular motions. The draw-tube is 

 also tapped at its lower end with the ordinary objective thread, to receive 

 when required a photographic correcting lens, to correct the objective for a 

 picture 1 to 1^ metres distant. The stage and body-tube are fixed and do 

 not revolve round the optic axis. 



