334 Mr. Armstrong on the electrical Phcenomena 



but under these circumstances I could detect no electrical de- 

 velopment beyond what was attributable to the combustion of 

 the fuel, which always produced sufficient electricity in the 

 evaporating apparatus to affect the gold leaves of the electro- 

 scope, when a condensing plate was used. I then restored 

 the valve, and when the pressure scarcely exceeded one pound 

 on the square inch, the gold-leaf electroscope, connected with 

 the boiler, gave the first indication of electricity distinguish- 

 able from that produced by combustion. The slightest ad- 

 dition to this pressure caused an excessive increase of electri- 

 city, and at three pounds on the square inch, small sparks 

 could be drawn from the boiler at the rate of five or six in a 

 minute. After this each successive equal increase of pressure 

 produced a less augmentation of electricity than the prece- 

 ding one. I should say that the electricity manifested at three 

 pounds on the square incli, was not doubled until the press- 

 ure became fifteen pounds per square inch ; not trebled until 

 it reached fifty pounds ; not quadrupled until it was raised to 

 120 pounds; and that when the pressure was augmented to 

 250 pounds on the inch, which was as high as I ventured to 

 carry it, the electricity of the boiler did not appear to be more 

 than five times greater than at a pressure of only three pounds 

 on the inch. Such were the results I obtained ; but as the 

 causes which tend to produce the opposite electrical states of 

 the boiler and steam-cloud were probably not altogether 

 quiescent in these experiments, the effects might possibly have 

 been different, if the apparatus had been so constructed as to 

 be more or less favourable to the operation of such causes. 

 The feebleness of the electricity evolved by the steam dis- 

 charged from Perkins's gun*, is probably owing to a counter- 

 acting agency of the nature I have mentioned ; and the varia- 

 tion which has been observed in the intensity of the electrical 

 effects, produced by the steam discharged at similar press- 

 ures from different steam-engine boilers, may be explained 

 upon the same principle. 



When circumstances were such as to render the electrical 

 states of the boiler and steam-cloud the reverse of what they 

 usually are, the effects of pressure were exceedingly incon- 

 gruous and perplexing. 



* I presume it has been tried whether the steam from Perkins's gun is 

 positive or negative ; but if not, I recommend the trial to be made, and I 

 thinic it possible that the electricity may prove to be negative; especially if 

 the pressure be run down a little and the steam not permitted to escape 

 very rapidly. The condensation which must take place in the gun-barrel will 

 be unfavourable to a development of electricity, and the steam ought, 

 therefore, to be discharged, it practicable, by some other means. 



