FAKMEES' INSTITUTES. 249 



Avas not better than a copper rod,*' and it is fair to presume that his answer was 

 made witli reference to the question asked. He says : "The ^hai^e of the con- 

 ductor is immaterial, provided the substance and quality of the metal are the 

 same." 



Prof. Miller, in speaking of experiments in galvanic electricity, in which case 

 the repulsive energy is so small that it pervades the whole body, says: '''It 

 therefore makes no difference whether the metal is in the form of a wire" (he 

 is not speaking of a lightning-rod), "or is extended over large surface as leaf." 



Deschanel, of France, says : "There are two exceptions to the rule that elec- 

 tricity isconfined to the external surface of a conductor: 1. It does not hold 

 for electric currents. Wo shall see hereafter, in connection Avitli galvanic elec- 

 tricity, that the resistance -which a Avire of given length opposes to the passage 

 of electricity through it dej^ends not upon its sectional area. A hollow Avire 

 Avill not conduct electricity so Avell as a solid wire of the same external diameter." 

 Natural Philosophy, j). 525. 



It Avill be noticed that he speaks of exceptions to the rule that electricity is 

 confined to the external surface of a conductor. While thus confirming the 

 general rule of surface conduction, he states the exceptions to be in the case of 

 galvauic electricity. He is here in harmony Avith other great teachers upon this 

 subject, including Prof. Henr}', as aa'C shall haA'e occasion to shoAV before Ave 

 liaA^e done Avitli this subject. 



The elementary proposition quoted from De la Rive, of Switzerland, is a aa'cII- 

 knoAA'n, generally admitted, and noAvhere questioned fact, viz. : that the larger 

 the Avire the more electricity it aviII convey ; and that a long Avire Avill not con- 

 duct the same amount of electricity Avith a short one of equal size. The same 

 rule Avould undoubtedly hold good Avitli regard to a lightning-rod, viz. : the 

 larger the rod the greater the capacity, and the longer the rod of equal size the 

 less its efficiency. 



Of Prof. Henry he again says, before quoting him as to the form of a cheap 

 and efficient lightning-rod, "Prof. Joseph Henry, secretary and director of the 

 Smithsonian institution at Washington, the highest authority on electricity in 

 this country." I will not copy his quotation; there is no issue between Dr. 

 Kedzie and myself as to the efficiency of a f-inch rod ; but I ask your readers 

 to notice the fact stated by Dr. Kedzie, that Prof. Henry is the highest author- 

 ity upon this subject in this country. 



The issue between Dr. Kedzie and myself is distinctly made in my article of 

 the 25th ult., Avhere I quote from him as follows : "The extent of surface in a 

 rod has no connection with its conducting power," and "' electricity does not 

 pass upon the surface of the conductor," and "that a round rod solid in form 

 Avill conduct an equal amount of electricity with that of a hollow tube contain- 

 ing the same amount of metal, but a largely increased surface." 



The doctor says, in reply to my article of the 25th : " Most of the authorities 

 quoted by Mr. Lanphere to sustain his position, that electric conduction is a 

 surface action, and that it does not pass through the mass of the metal in a 

 conductor, are treating of static electricity, or electricity standing still, and not 

 of electricity in motion." Can he be candid in this statement? Let us see. 



Prof. Silliman of Yale College, a man Avho has no superior as authority in 

 matters of this kind, defines static electricity as folloAA^s : "Bodies in their nat- 

 ural state giA'e no OA'idence of its presence, but by different means it may be 

 evoked from all. Hence statical electricity implies that condition of this subtle 

 ^ther resting in all bodies in a state of electrical quiescence. Statical electricity 

 32 



