948 Transactions of the American Institute. 



aurora boreiilis should be a daily phenomenon, more or less mtense; 

 consequently, visible at greater or less distances, and only when 

 nights are clear; which is perfectly in accordance with observation." 

 The electric origin of the aurora being conceded, it follows as a 

 natural deduction from the statement of De la Rive that the elec- 

 tric disturbance may be such as to affect a telegraphic wire even 

 when no aurora is visible. Other causes have been assigned for 

 the apparently spontaneous generation of electricity on telegraphic 

 wires. In this connection, we present the following article in the 

 Journal of the Telegraph, from the pen of Charles E. Pomeroy, 

 agent of the Western Union line at Great Salt Lake city, Utah: 



FRICTIONAL ELECTEICITY EXCITED BY THE AIR. 



A curious electrical phenomenon occurred several times upon the 

 Overland Telegraph line, of which the following brief description 

 is given: 



It has happened three or four times within, three years, that a 

 strong, steady northwest wind blew from Fort Laramie, Dakotah, 

 to Omaha, Nebraska, a distance of six hundred miles. This current 

 of wind arose during the forenoon, and increasing rapidly toward 

 noon, attained its greatest velocity at 2 p. m., at which time a 

 powerful current of electricity, excited by the friction of the air 

 upon the wire, was observed to flow into the Omaha office, changing 

 the circuit to so great an extent as to entirely suspend communica- 

 tion, and heating the relay magnet to a degree which rendered it 

 necessary to cut it out from the circuit at the thumb screws. 



The main battery being thrown out of the circuit, the key was 

 opened, when a large and remarkably'" vivid spark, of an intensely 

 brilliant purple hue, appeared at the platina points of the key. 

 The point of a penknife blade, which was inserted in the spark, 

 was instantly fused. The spark continued uninterruptedly for 

 several minutes, when, it being feared that the platina points would 

 be destroyed, the key was opened to one-quarter of an inch play, 

 notwithstanding which the spark increased proportionably in size 

 and brilliancy, and remained unbroken. A bit of charcoal placed 

 between the points of the key was almost instantly decarbonized 

 and reduced to ashes. A small lump of blue vitriol was then 

 introduced into the spark, and was immediately ignited, exhibiting 

 a bluish flame, but being reduced to ashes less quickly than the char- 

 coal; a common lead pencil being interposed, was instantaneously 

 ignited and rapidly burned through, with a flame of a reddish tint. 



