100 The Rev. S. Earnshawow some Remarks o/Dr. Le Conte 



different types with different velocities. On the contrary, they 

 show that the difference of velocities is a strictly legitimate and 

 necessary consequence of the difference between the wave-types, 

 one being exponential and the other circular ; and it is in fact 

 exactly analogous to this — viz. that |(e*+e - *) can never be less 

 than 1, and ^(e'^i + e-'^) never greater than 1, whatever 

 value be given to x. It arises from this that the velocities of 

 transmission of one type of wave range from V to infinity, and 

 those of the other type from V to 0. I hope that after this ex- 

 planation Dr. Le Conte will not continue to think that my 

 " results set at nought all our physical conceptions/'' and will 

 agree with me in believing that they are very natural conse- 

 quences of the physical hypotheses from which they follow, and 

 open to us a new field of wonder and admiration in the world of 

 sound. He seems to have formed an opinion, based on his notion 

 of what an almost physical impossibility is, that my results belong- 

 to a class of mathematical fictions. I can assure him that they 

 are strictly deduced from the original physical assumptions; and 

 therefore if there is any fiction in the matter it must lie, not in 

 the mathematical results, but in the physical hypotheses from 

 which they are deduced; and those hypotheses are— 



1. That the atmosphere is a medium of separate molecules; and 



2. That the molecular force varies according to the inverse 

 third power of the distance. Perhaps Dr. Le Conte will be now 

 satisfied that there is not much fiction in the matter. 



But as I supported my results, so far as they differ from pre- 

 viously received opinions, by reference to certain physical facts, 

 Dr. Le Conte next proceeds to discredit my facts. He refers to 

 the velocity with which the sound of thunder-claps is transmitted, 

 which according to my theory ought to be greater than that of 

 ordinary sounds. He disposes of my facts about thunder-claps 

 by remarking that flashes of lightning are sometimes several 

 miles in length, and that " the observer estimates one element 

 for determining the velocity, viz. the distance, under the assump- 

 tion that the sound is generated at the point struck by the elec- 

 tricity." Now I will grant that an inexperienced and ignorant 

 observer might do this ; but my facts were furnished to me by 

 Professor C. Montigny, who knew a great deal better what he 

 was doing than to fall into such a learner's mistake. Besides, it 

 is quite plain that Dr. Le Conte has never considered the nature 

 of the evidence. Let us take one of Prof. Montigny's facts. 

 There were two observers, who were about equidistant from each 

 other and from the point struck. That distance was such that, 

 according to the common theory, it would take sound about 15 

 seconds to go from one to the other. Now Dr. Le Conte shall 

 have a flash of lightning as long as he likes, and I ask him to 



