SMOKING CHAMBER. 



207 



glazed surface down, on the table ; wrap it evenly round the cylinder, 

 and fasten it on tightly by means of the gummed edge after the manner 

 of a newspaper wrapper. 



Smoke the surface of the paper. A special chamber (Fig. 36), which 

 prevents access of smoke to 

 the room, is provided in the 

 wall of the laboratory. 



Take the spindle A from 

 the chamber, mount the 

 drum upon it, clamping 

 screw to the right, and 

 place in the chamber. 



Uncover and light the 

 wick (6 inch) of the lamp 

 beneath the smoking cham- 

 ber, adjust the flame so as 

 to cause a uniform sheet 

 of smoke to play upon the 

 paper. Close the door C 

 of the chamber, revolve 

 the cylinder at about once 

 a second. Inspect through 

 the door from time to time, 

 and extinguish the flame 

 when the paper is uniformly 

 covered with a deep brown 

 covering of soot. The cover- 

 ing must not be thick on 

 account of the resistance 

 which it offers to the writing 

 point. Therefore stop short 

 of complete blacking. 



Injury to the blacking 

 on the cylinder when with- 

 drawing it from the chamber 

 is prevented by the guides. 



The natural draught may be so great that it may be necessary to keep the aperture 

 at D open. In case of a down draught there is a ring burner in D, by means of which 

 the upward current can be ensured. 



The chronogram. Though a time tracing may be inscribed by 

 means of a point attached to a tuning fork or other oscillator, writing 

 directly upon the recording surface, an electrically driven style is the 



FIG. 36. Smoking chamber. 



