attending the Bfflu.v of condensed Air and Steam. 329 



impart peculiar Interest to the inquiry, and rentier it woi thy 

 of zealous pursuit. 



In the hope, therefore, of promoting an investigation which 

 appears to me to possess so much interest and iniportance, I 

 have recently undertaken a series of additional experiments, 

 both on the electricity of expanding air, and on that of efflu- 

 ent steam, and I trust that the resuUs which I have now to 

 communicate will be found deserving of attention, and condu- 

 cive to further discovery. 



These experiments will be treated in the following pao'es 

 under two heads ; the first embracing the experiments°on ex- 

 panding air, and the second those on effluent steam. 



In my last communication to the Philosophical Magazine* 

 I stated— " 



1st, That I had succeeded in producing a powerful elec- 

 trical development by discharging highly compressed air from 

 an insulated receiver of considerable capacity, 



2ndly, That on repeating the experiment a great number 

 of times, I found the electricity manifested in the receiver to 

 be generally negative, but occasionally j^ositive. 



Srdly, That the intensity of the development had proved 

 exceedingly unequal, the receiver having sometimes been so 

 highly electrified as to yield a spark a quarter of an inch lono-, 

 while at other times its electricity had been feeble, and that 

 frequently I could detect no electricity at all. 



4thly, That the electricity of the emitted air had been posi- 

 tive in every instance that I had tried it. 



5thly, That I had more frequently succeeded in producino- 

 an electrical development when the receiver was cold, and 

 contained a little moisture, than when it was warm and dry. 



Having thus briefly recajjitulated what I have already 

 written on the subject, the necessity of referring to the com- 

 munication I have mentioned will be avoided. 



I have now clearly ascertained that the temperature of the 

 receiver, and the presence of water within it, powerfully in- 

 fluence the phasnomena. The colder the receiver the strono-er 

 is the development of electricity; and if the receiver, when 

 perfectly dry, be heated until it becomes unpleasantly hot to 

 be touched with the naked hand, the discharge of the air 

 ceases to produce any indication of electricity. If the inside 

 of the receiver be damp, a higher temperature is required to 

 obliterate the signs of electricity ; and if a few ounces of water 

 be poured into the receiver, it may be heated to any dcn-ee 

 without preventing an electrical development, or even render- 

 ing it very inconsiderable. At low temperatures, however, 

 the presence of water in the receiver, or a humid condition of 

 * Number for February, p. 133. 



