1846] WRITINGS OF JOSEPH HENRY. 251 



heavens ; and the phenomena which I witnessed on the 19th 

 of June in the telegraph office in Philadelphia were, I am 

 sure, of this kind. In the midst of the hurry of the transmis- 

 sion of the congressional intelligence from Washington to 

 Philadelphia, and thence to New York, the apparatus began 

 to work irregularly. The operator at each end of the line 

 announced at the same time a storm at Washington, and 

 another at Jersey City. The portion of the circuit of the 

 telegraph which entered the building, and was connected 

 with one pole of the galvanic battery, happened to pass 

 within the distance of less than an inch of the wire which 

 served to form the connection of the other pole with the 

 earth. Across this space, at an interval of every few minutes, 

 a series of sparks in rapid succession was observed to pass ; 

 and when one of the storms arrived so near Philadelphia 

 that the lightning could be seen, each series of sparks was 

 found to be simultaneous with a flash in the heavens. Now 

 we cannot suppose, for a moment, that the wire was actually 

 struck at the time each flash took place ; and indeed it was 

 observed that the sparks were produced when the cloud and 

 flash were at a distance of several miles to the east of the 

 line of the wire. The inevitable conclusion is that all the 

 exhibition of electrical phenomena witnessed during the 

 afternoon was purely the effects of induction, or the mere 

 disturbance of the natural electricity of the wire at a distance, 

 without any transfer of the fluid from the cloud to the 

 apparatus. 



The discharge between the two portions of the wire con- 

 tinued for more than an hour, when the effect became so 

 powerful that the superintendent, alarmed for the safety of the 

 building, connected the long wire with the city gas pipes, and 

 thus transmitted the current silently to the ground. I was 

 surprised at the quantity and intensity of the current; it is 

 well known that to affect a common galvanometer with 

 ordinary electricity requires the discharge of a large battery; 

 but such was the quantity of the induced current exhibited 

 on this occasion that the needle of an ordinary vertical gal- 

 vanometer, with a short wire, and apparently of little sensi- 

 bility, was moved several degrees. 



