Conductor of Electricity. 15 



One of these platinum wires was then connected with the 

 outside of a Leyden jar, the other with an insulated discharger. 



The Leyden jar, containing about 100 square inches armed 

 surface, was now charged by means of fifty revolutions of a 

 twelve-inch glass plate, and then discharged through the tube 

 as usual. The glass tube acted exactly as an imperfect con- 

 ductor, interrupting the conducting wii'e, which connects the 

 two surfaces of the jai', like a piece of wet cotton thread, or 

 portion of glass tube moistened inside. The jar was perfectly 

 discharged by the first touch, with that peculiar hissing noise 

 and reddish fascicular stream of electricity which invariably 

 occur under similar circumstances. The temperature of the 

 sand-bath was now gradually raised, and at every 5 degrees 

 a similar electric discharge from the Leyden jar was passed 

 through the tube. The same results were obtained until the 

 thermometer reached 250 degrees. At this point, by dis- 

 charging the jar, a small red spark was obtained, instead of 

 the former fascicular stream, and the jar was found to be en- 

 tirely discharged, although the noise occasioned by the spark 

 was scarcely audible, compared with the loud clap produced 

 by the discharge of the jar under ordinary circumstances. 



After the temperature had been elevated to 405 degrees, 

 the contents of the jar discharged with the usual brilliant 

 spark and loud report, and at the same time the spark was 

 seen passing through the tube. At this time no moisture 

 could be detected in the tube, and the water-gas contained in 

 it had entirely ceased to be a conductor of electricity, at the 

 same time giving less resistance to the passage of the spark than 

 common air, the striking distance having been elongated from 

 half an inch to one inch and a quarter. When the tempera- 

 ture was reduced below 405 degrees, the discharge passed 

 as before mentioned, either as a small red spark, or in a fasci- 

 cular stream, according to the temperature. When above 

 405 degrees the spark passed as usual, until the temperature 

 rose to 443, when the tube burst, which prevented me from 

 ascertaining its weight with and without the water ; the differ- 

 ence of which would of course have given me the weight of 

 the water contained in the tube, the cubical contents of which 

 would have been ascertained by filling it with quicksilver. 

 If we assume that there were two drops of water in the tube 

 when it burst, weighing together 0*73 grains, and supposing 

 the contents of the tube to be 500 cubic lines, we have the 

 pressure of 23*5 atmospheres therein. 



laboratory and philosopliical apparatus for the purpose of making these 

 experiments. Institutions of this description, which are to be found only 

 in England, are invaluable to foreigners occupied in philosophical re- 

 searches. 



