34 



ELEMENTARY CHEMICAL MICROSCOPY 



place, as shown in Fig. 10. Accompanying the instrument is a 

 rheostat so constructed as to permit the lamp to be connected 



with ordinary house- 

 lighting circuits. One 

 of the great advantages 

 of this illuminating 

 device is the rapidity 

 with which it can be 

 attached or removed 

 from the microscope. 

 The radiant being self- 

 contained there is no 

 loss of time or annoy- 

 ance of properly " lin- 

 ing up " the source of 

 light. 



The Silverman Illu- 

 minator may also be 

 used with microscopes 

 of the Greenough dou- 

 ble objective type. For this purpose a clamp, Fig. n, is pro- 

 vided which fastens to the stage of the microscope. The fingers 

 are held back by a ring R, attached to the spindle of the clamp; 

 there is thus afforded an unobstructed view through the central 

 orifice. The lamp and mounting are adjusted below the objective 

 so as to interfere in no way with the field of view. Unless the 

 worker is left handed the clamp should be fastened on the left side 

 of the stage and as far back toward the pillar as possible so as not 

 to interfere with manipulations which may be made upon the 

 stage. 



The character of the light rays thrown by the Silverman 

 Illuminator is similar to those reflected by the old time para- 

 boloid save that they more nearly axial, in other words the 

 light effect is that of a combination of both axial and oblique 

 rays streaming from an incandescent filament in the form of 

 a semicircle. This will be readily understood by referring to 

 Fig. 12. The dotted lines a, a' mark the points of attachment 



Fig. io. The Silverman Illuminator attached to 

 the Objective of the Microscope. 



