FAKMEES' INSTITUTES. 251 



these views ''old and antiquated," as tliey were published some years ago, I 

 addressed a communication to Prof. Henry, under date of Feb. 5, asking his 

 present views upon the subject in controversy between Dr. Kedzie and myself, 

 in which the following questions were asked : 



1. Does a lightning-rod acting as a silent conductor, and in the absence of 

 an explosive discharge, conduct the electricity mainly upon its surface? 2. In 

 case of an explosive discharge upon a rod of sufficient capacity, does the elec- 

 tricity pass mainly upon the surface in its passage to the earth? 3. Will a 

 metallic tube conduct more atmospheric electricity (or lightning) than a solid 

 rod containing only the same amount of metal? 



Under date of Feb. 9 I received the following reply to my inquiries : 



Smithsonian Institute, } 



Washington, D. C, 2c1, 9th, 1876. ) 



Dear Sir, — In answer to your inquiries of the 5th inst., I have to state the 

 following : 



1. Atmospheric electricity, or that of great tension or repulsive energy, passes 

 at the surface of a conductor, Avhether the discharge be silent or explosive. In 

 the second case it is charged for an instant as it were by a wave of electricity, 

 and tends to give off minute sj)arks to a conductor brought near it, however per- 

 fectly it may be connected with the earth. 2. This is answered by the first. 

 3. A given quantity of metal in the shape of a liollow tube will offer less resist- 

 ance to a discharge of atmospheric electricity than the same amount of metal 

 in the form of a solid cylinder. In galvanic electricity the repulsive energy 

 is so small that the electricity pervades the whole mass, and hence the result 

 obtained by experiments on the latter should not be applied to atmospheric 

 electricity, in whicli the repulsive energy exists in the highest degree. 



Truly yours, etc., 



Joseph Hexrt, Sec'y. 



A. T. Lanpiiere, Coldwater, Midi. 



As Dr. Kedzie has pronounced Prof. Henry the highest authority on electric- 

 ity in this country, this letter would seem to be conclusive as between the doc- 

 tor and myself. Yet, as he says, "I did not quote authorities to sustain my 

 position because this [his] theory is now so generally received by scientific men 

 that I did not think it necessary to quote authorities," I desired, if possible, to 

 ascertain who, if any, among our scientific men shared his opinion upon this 

 subject. With this view I addressed communications, similar to that sent to 

 Prof. Henr}-, to Prof. Douglas of the Michigan University; Prof. Thomas Hill, 

 M. D., late president of Harvard University, Cambridge; Prof. Edward You- 

 mans; Prof. Benj. Silliman Jr., of Yale Gollege ; Prof. Joseph Levering of 

 Cambridge, and many others of our scientific men ; and from the answers that 

 have been received, almost uniform in their tone of opposition to Dr. Kedzie' s 

 theory, I will select three only, as this article is already longer than I intended 

 it should be, reserving others for future use should the autliorities quoted here- 

 in be pronounced ''old and antiquated." 



Prof. Douglas, under date of Feb. 12, says: "Yours is received and con- 

 tents noted. I answer a? follows: 1. The electricity is conducted on the 

 exterior surface. 2. The passage is upon the exterior surface." He further 

 recommends gas-pipe (being a hollow tube) for efiiciency in the construction of 

 a lightning rod. 



