on the Wires of the Electric Telegraph. 193 



sity and quantity, that all the wires across which it passed 

 were melted at points in the same straight line as if they had 

 been cut in two by a sharp knife. 



The effects of the powerful discharges from the clouds may 

 be prevented in a great degree, by erecting at intervals along 

 the line, and aside of the supporting poles, a metallic wire, 

 connected with the earth at the lower end, and terminating 

 above at the distance of about half an inch from the wire of 

 the telegraph. By this arrangement the insulation of the con- 

 ductor will not be interfered with, while the greater portion 

 of the charge will be drawn off. I think this precaution of 

 great importance at places where the line crosses a river, and 

 is supported on high poles ; also in the vicinity of the office 

 of the telegraph, where a discharge, falling on the wire near 

 the station, might send a current into the house of sufficient 

 quantity to produce serious accidents. The fate of Prof. Rich- 

 man, of St. Petersburg, should be recollected, who was killed 

 by a flash from a small wire, which entered his house from an 

 elevated pole while he was experimenting on atmospheric 

 electricity. 



The danger, however, which has been apprehended from 

 the electricity leaving the wire and discharging itself into a 

 person on the road, is, I think, very small; electricity of suf- 

 ficient intensity to strike a person at the distance of eight or 

 ten feet from the wire, would, in pi'eference, be conducted 

 down the nearest pole. It will, however, in all cases be most 

 prudent to keep at a proper distance from the wire during the 

 existence of a thunder-storm in the neighbourhood. 



It may be mentioned as an interesting fact, derived from 

 two independent sources of information, that large numbers 

 of small birds have been seen suspended by the claws from 

 the wire of the telegraph. They had in all probability been 

 instantaneously killed, either by a direct discharge, or an in- 

 duced current from a distant cloud, while they were resting on 

 the wire. 



Though accidents to the operators, from the direct dis- 

 charge, may be prevented by the method before mentioned, 

 yet the effect on the machine cannot be entirely obviated ; the 

 residual current which escapes the discharge along the per- 

 pendicular wires, must neutralize for a moment the current 

 of the battery, and produce irregularity of action in the appa- 

 ratus. 



The direct discharge from the cloud on the wire is, com- 

 paratively, not a frequent occurrence, while the dynamic in- 

 ductive influence must be a source of constant disturbance 



