ELECTRICITY IN THUNDER-STORMS. 693 



steam was freely escaping, and then advancing the other hand toward any con- 

 ducting body, sparks of about an inch in length were obtained. But it was 

 soon observed that, by elevating the rod in the steam, the electricity was gradu- 

 ally increased, and that the maximum effect was not obtained until the end of 

 the rod was raised five or six feet above the valve, at which point the length of 

 the sparks occasionally reached two inches. Small sparks were even obtained 

 when the rod was wholly removed from the steam and held in the atmosphere 

 at the distance of two or three feet from the jet ; and the electricity thus drawn 

 from the air was positive like that of the steam. When the rod was extended 

 into the cloud of vapor which accumulated in the upper part of the shed, elec- 

 tricity was drawn down as by a lightning-conductor from a thunder-cloud." 



These results seem to me to point out very clearly the cause of the 

 electrical excitement. If it were the friction of steam against the sides 

 of the exit-pipe, then at that point should be the greatest manifesta- 

 tion. If, on the contrary, it be condensation, then at a distance from 

 the exit, where the greatest condensation takes place, should be the 

 greatest development and such is the fact. At the valve, Faraday 

 found no electricity. At five or six feet from it, according to Arm- 

 strong and to Patterson, its development was abundant. The conclu- 

 sion seems to me inevitable. All the facts point to condensation as 

 the cause of the excitement. 



A phenomenon that occurs daily at Pike's Peak has been described 

 to me. The tops of the mountain, are covered with perpetual snow. 

 During the summer months the snow-line gradually recedes up the 

 sides of the mountain, and from it flow considerable streams of water, 

 that are finally lost in the plains below. The winds coming from the 

 prairies take up this moisture, and, ascending the mountain, reach the 

 frozen regions above. At about eleven o'clock each day, black clouds 

 begin to gather about the tops of the mountain, and soon thereafter 

 pour down floods of rain. Flashes of lightning are almost incessant, 

 with peals of thunder that seem to shake the mountains. I am in- 

 formed that we have nothing in Eastern States that can compare with 

 the terrific violence of these storms. 



Here, certainly, is no friction, but condensation on a large scale ; 

 and it is attended with the same electrical effects that were observed in 

 the condensation of steam from the steam-boiler. 



Volcanoes sometimes emit great volumes of steam and smoke, and 

 these are usually attended with flashes of lightning in every direction. 

 Were the electricity due to friction, it would be found at the mouth of 

 the crater, where the steam issues; but, instead of that, it is found on 

 the sides of the column, where the steam meets with colder air, and is 

 condensed to water. The effects are analogous in every respect to 

 those of steam from the steam-boiler. 



In thunder-storms we have no friction, but condensation, and we 

 need not go beyond the usual effects of condensation to explain all the 

 electrical phenomena. 



