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road near the conducting wires, the telegraph will very probably soon 

 be demolished, and might not easily be again renewed. 



Will you have the goodness to present this subject to the considera- 

 tion of the Philosophical Society, and invite the attention of the mem- 

 bers to it; and accept the assurance of the very great respect of 



Your most obedient. 

 Dr. RoBT. Patterson. S. D. INGHAM. 



Professor Henry, to whom the foregoing letter was referred, 

 made the following report: — 



The action of the electricity of the atmosphere on the wires of the 

 electrical telegraph, is at the present time a subject of much import- 

 ance, both on account of its practical bearing, and the number of 

 purely scientific questions which it involves. I have accordingly 

 given due attention to the letter referred to me, and have succeeded 

 in collecting a number of facts in reference to the action in question. 

 Some of these are from the observations of different persons along 

 the principal lines, and others from my own investigations during a 

 thunder storm on the 19th of June, when I was so foiiunate as to be 

 present in the office of the telegraph in Philadelphia, while a series 

 of very interesting electrical phenomena was exhibited. In con- 

 nexion with the facts derived from these sources, I must ask the in- 

 dulgence of the Society in frequently referring, in the course of this 

 communication, to the results of my previous investigations in dy- 

 namic electricity, accounts of which are to be found in the Pro- 

 ceedings and Transactions of this Institution. 



From all the information on the subject of the action of the elec- 

 tricity of the atmosphere on the wires of the telegraph, it is evident 

 that effects are produced in several different ways. 



1. The wires of the telegraph are liable to be struck by a direct 

 discharge of lightning from the clouds, and several cases of this kind 

 have been noticed during the present season. About the 20th of May 

 the lightning struck the elevated part of the wire, which is supported 

 on a high mast at the place where the telegraph crosses the Hacken- 

 sack river. The fluid passed along the wire each way from the point 

 which received the discharge, for several miles, striking off at irre- 

 gular intervals down the supporting poles. At each place where the 

 discharge to a pole took place, a number of sharp explosions were 

 heard in succession, resembling the rapid reports of several rifles. 

 During another storm, the wire was struck in two placves in Pennsyl- 



