FRAGMENTS OF SCIENCE. 



A glass tube 3 feet long and 3 inches wide, which had 

 been frequently employed in my researches on radiant 

 heat, was supported horizontally on two stands. At one 

 end of the tube was placed an electric lamp, the height 

 and position of both being so ar- 

 Fie.2. ranged that the axis of the tube, 



and that of the beam issuing from 

 the lamp, were coincident. In the 

 first experiments the two ends of 

 the tube were closed by plates of 

 rock-salt and subsequently by plates 

 of glass. For the sake of distinc- 

 tion, I call this tube the experi- 

 mental tube. It was connected with 



an air- 



pump, 



and also with a series 



of drying and other tubes used 

 for the purification of the air. 



A number of test-tubes, like F, 

 fig. 2 (I have used at least fifty 

 of them), were converted into 

 AVoulf s flasks. Each of them was 

 stopped by a cork, through which 

 passed two glass tubes: one of these 

 tubes (a) ended immediately below 

 the cork, while the other (b) de- 

 scended to the bottom of the flask, 

 being drawn out at its lower end to 

 an orifice about 0.03 of an inch in 

 diameter. It was found necessary 

 to coat the cork carefully with 

 cement. In the later experiments 

 corks of vulcanized india-rubber 

 were invariably employed. 



The little flask, thus formed, being partially filled with 

 the liquid whose vapor was to be examined, was introduced 

 into the path of the purified current of air. The experi- 

 mental tube being exhausted, and the cock which cut off 

 the supply of purified air being cautiously turned on, the 

 air entered the flask through the tube b, and escaped by 

 the small orifice at the lower end of b into the liquid. 

 Through this it bubbled, loading itself with vapor, after 

 which the mixed air and vapor, passing from the flask by 

 the tube a, entered the experimental tube, where they 

 were subjected to the action of light. 



