334 DRAWING WITH PROJECTION MICROSCOPE [Cn. X 



h 



FIG. 1 86. 



APPARATUS FOR DRAWING WITH THE MICROSCOPE WITHOUT 

 AN OCULAR OR SUBSTAGE CONDENSER. 



The arc'lamp is Mr. Albert T. Thompson's automatic lamp for direct current, 

 5-25 amperes. This is the first automatic arc lamp for right-angled carbons. 



By means of the optical bench carrying all the apparatus, the different 

 parts are pulled forward so that the microscope tube and mirror project over 

 the drawing shelf. This is adjustable up and down for varying the magnifi- 

 cation. 



The stage of the microscope (st) is independent and contains a large glass 

 water-cell against which the specimen rests. It conducts away the heat from 

 the specimen. 



a a a Optic axis. 



b Optical bench with track. 



c Triple condenser with water-cell. 



/ Thompson's automatic arc lamp for 5-25 amperes direct current. 



m Microscope without ocular. The 45 mirror reflects the light down upon 

 the drawing surface. 



r Adjustable rheostat. 



s Double-pole knife switch (table switch). 



st Stage with the stage water-cell for cooling the specimen. The stage is 

 entirely separate from the microscope. 



sh Shield 25 cm. in diameter to stop any stray light from the stage of the 

 microscope. 



wi Double cable supplying the electric current to the apparatus. 



W2 Flexible cables from the switch to the lamp. 



