Mr. W. G. Armstrong on ihe Electricity of Effluent Steam. 53 



by reference to the figure. The cylinder, and a great part of 

 each of tlie tubes, were enveloped in flannel, so as to prevent 

 condensation as much as possible. The chief object of this 

 apparatus was to test the electrical condition of the steam be- 

 fore it issued into the air, both when the boiler was insulated 

 and when it was connected by a conductor with the earth. 

 An iron bar was then placed against the engine to establish a 

 communication between it and the ground, and the cock being 

 opened, a current of steam mixed with water issued from the 

 tube E. Under these circumstances both pairs of balls re- 

 mained stiitionary, the electricity being probably carried ofF 

 by the water which escaped with the steam. As the tubes 

 became heated the quantity of water discharged with the steam 

 was reduced to a mere spray, and both pairs of balls then 

 slightly diverged with positive electricity, the upper pair ex- 

 panding rather more than the lower pair ; but upon partially 

 closing the cock both pairs of balls expanded fully three times 

 as much as they had done when the cock was fully open ; and 

 then gradually converged, arriving at their original position 

 after tiie lapse of about a minute. 



1 was at first exceedingly puzzled how to account for this 

 singular effect of attenuating the steam, but I now think it 

 may be explained as follows. It is probable that the moisture 

 of the steam when the cock is fully open is sufficient to enable 

 it to conduct great part of the electricity of the jet back again 

 to the boiler; but that as soon as the temperature of the steam " 

 is reduced by the attenuation below the temperature which 

 the tubes have previously acquired from the high-pressure 

 steam, its dryness is so far increased as to prevent the trans- 

 mission of electricity from the jet to the boiler, but not from 

 the jet to the cylinder, which is a much nearer object. As the 

 tubes cool down to an equality with the steam the dampness 

 returns, and the electricity is again in a great measure carried 

 back to the boiler. 



The iron bar was then removed from its contact with the 

 boiler so as to restore the insulation, and the engine was ren- 

 dered intensely negative by a copious emission of steam from 

 the safety-valve. The cock being again fully opened, both 

 pairs of balls diverged strongly with negative electricity; and 

 by diminishing the escape from the valve to a certain point, 

 and then partly closing the cock, the upper balls indicated 

 2)0sitive, and the lower ones negative electricity. When the 

 escape from the valve was entirely ])revented and the cock 

 fully opcncfl, both i)airs of balls remained in a collapsed state, 

 but on partly opening the cock they both diverged lor a short 

 time with positive electricity to much the same extent as they 



