72 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



mospheric currents were interfering with the working of the 

 telegraph lines. These currents increased in intensity to an 

 almost unprecedented extent, and then died away during the 

 evening. 



At 6:45 P. M. these disturbances were noticed at the offices 

 in the Mississippi Valley separating Iowa from Illinois. 



At 9:30 P. M. light disturbances were noted at Chicago, 

 and continued at intervals during the night and until the 

 evening of the 8th, when the discharges became very rapid 

 and intense. It was now ascertained that the phenomena 

 had entirely ceased in the MississijDpi Valley, and that the 

 region of disturbance was jirobably central at Chicago and 

 eastward. Here, as before, with two or three exceptions, 

 the effect was confined to wires running due east and w'est, 

 the exceptions being the north and south lines, on which, 

 however, but little interference was noticed. 



Later in the evening of the 8th, the disturbance was felt 

 at Detroit, Michigan, and "every observation confirmed the 

 opinion" that the central path of the storm extended "from 

 Des Moines, Iowa, due eastward to Detroit, Michigan, nar- 

 rowing its limits north and south as it approached the latter 

 place, after which it rapidly subsided." 



It is well known that in all these observations there is 

 o-enerally some doubt as to the interpretation of the observa- 

 tions, owing to our ignorance of the state of insulation, etc., 

 of the telegraph wires. In the present case, however, Mr. 

 Simmons appears to have made accurate observations rela- 

 tive to this point, since he states that w^hile the east and 

 west wires were almost exclusively afiected, the known re- 

 sistance and insulation of these lines, in reference to the prop- 

 agation of ordinary voltaic electricity, did not in the least 

 assist to explain the observations. Indeed, he states that 

 the large number of operators and practical telegraph men 

 who witnessed the display quite agree that the effects were 

 entirely different from those experienced during the ordinary 

 auroral storms w^ith which they are familiar. 



It is therefore probable that the present is a case of at- 

 mospheric electricity as distinguished from that known as 

 ground currents, the latter being connected with auroral dis- 

 plays. While the phenomena of January 7-8 were evidently 

 concomitants of the storm that prevailed from Minnesota to 



