86 



ELEMENTARY CHEMICAL MICROSCOPY 



of the radiant. To obviate this defect Tassin has devised an 

 apparatus in which the radiant either a small tungsten lamp 

 or an acetylene burner is attached to the illuminator mount- 

 ing and hence in focusing, both radiant and illuminator are 

 displaced simultaneously an equal amount; thus no realign- 

 ment is necessary. The construction of this device will readily 

 be understood by referring to the diagram, Fig. 37. An ordi- 

 nary disk (or prism) illuminator I is attached to the tube T of 



FIG. 37. Tassin Vertical Illuminator. 



the microscope. Into the lower opening is screwed an aluminum 

 adapter A which serves to hold in position the supporting bar 

 B. The objective O is screwed into the lower end of A. The 

 bar B carries a vertical sleeve J, fitted with a thumb-screw and 

 serving to hold in place the remaining parts of the illuminator. 

 The sleeve D carries a Ramsden eyepiece, securely held in posi- 

 tion by the screw K. This eyepiece acts as a condensing lens. 

 The correct position of the lenses to obtain a spot of bright light 

 of the requisite diameter upon the reflecting surfaces is secured 



