330 Mr, Armstrong on the electrical Phcenomena 



the compressed air, appears to have little tendency to aug- 

 ment the effects. This I infer from the following experi- 

 ment. 



After thoroughly drying the interior of the receiver I intro- 

 duced a quantity of caustic potash for the purpose of absorb- 

 ing the moisture of the condensed air. I then charged the 

 receiver, and set it in a cold place, where I allowed it to re- 

 main for about twelve hours, to afford sufficient time for the 

 potash to produce the desired effect. After this I insulated 

 the receiver and discharged the air, and found the effects to 

 be nearly the same as when no precautions were taken to ex- 

 clude moisture. 



Whether the receiver be wet or dry, I find that a rapid 

 discharge of the air is indispensable to the production of the 

 phenomena. The effects are always strongest when the cock 

 for discharging the air is fully opened ; and when by only 

 partially opening the cock the emission of the air is prolonged 

 beyond the period of about a minute, no electricity appears to 

 be developed. 



My former experiments, of which the results were so ex- 

 ceedingly capricious, were made in very frosty weather, but 

 those of which I am now speaking were made when the 

 weather was mild and damp, and were much more uniform in 

 their results; but whether the singular fluctuations observed 

 in the first set of experiments were owing to the state of the 

 atmosphere, or to some other cause which has escaped my 

 detection, I feel quite unable to say. 



In my latter experiments the electricity of the receiver was 

 uniformly negative, and the intensity of the electrical develop- 

 ment did not vary considei'ably. When the receiver was not 

 insulated, the electricity of the effluent air was always posi- 

 tive; but when the receiver was supported upon an insulated 

 stand, it frequently happened, especially if the receiver were 

 not internally dry, that the gold leaves of the electroscope 

 connected with the pointed conductor, by which the electri- 

 city was drawn from the jet of air, separated, first with jiositive 

 electricity, then closed, and opened with negative electricity. 

 This effect might, with much probability, be ascribed to the 

 formation of a conducting communication between the insu- 

 lated receiver and the pointed conductor, by means of watery 

 particles ejected with the air ; only, if this were the case, the 

 pointed conductor would not retain its electricity, as it inva- 

 riably does when the receiver is not insulated. 



Sometimes the development of electricity does not take 

 place until the air is almost wholly discharged, and then the 

 pith balls suspended from the receiver, and the gold leaves 

 of the electroscope attached to the pointed conductor, ab- 



