102 The Rev. S. Earnshaw on some Remarks of Dr. LeConte 



theory ; and Dr. Le Contc's assertion that I have not produced 

 a single fact confirmatory of my theory is disposed of. It is 

 not to be expected that I should be able to lay my hands on 

 many, or even on any, recorded observations made previous to 

 the publication of my papers on the subject, because previous to 

 that time experimentalists were under the conviction that all 

 sounds travel at the same rate. This had been rigorously 

 proved in the case of sounds of the musical type; and not 

 being aware of the duality of types, they took it for granted 

 that what was true of musical sounds was true of all sounds. 

 They did not look for any difference of velocities, therefore; and 

 the difference would have had to be very considerable before 

 they would take notice of it so as to make a record of it. 



Dr. Le Conte represents me as saying that " sound-waves em- 

 bracing velocities from JV to infinity are within the limits of 

 experimental verification." I simply deny that I have said so. 

 The spirit of my papers is directly opposed to such a state- 

 ment. Contrary to his assertion, I have carefully said that all 

 audible sounds travel with velocities equal to V and upwards 

 towards infinity; and Dr. Le Conte' s inference, that I ought to 

 be required to verify these velocities (fromVto jV) experimentally, 

 falls, like his other assertions, to the ground. Both Prof. Mon- 

 tigny and Captain Parry have testified that there are sounds which 

 travel with velocities not equal to, and exceeding, the velocity of 

 common sounds, which is all that I have asserted from my inves- 

 tigations. 



I should like to terminate my letter at this point ; but there 

 is one other remark of Dr. Le Conte' s which I must not leave 

 unanswered, because he evidently thinks he has put me on the 

 horns of a dilemma from which there is no escape for me. He 

 tells me that my theory takes no cognizance of the development 

 of heat, which I admit to be a vera causa. He is surprised that 

 I should have any confidence in a formula obtained without 

 taking any account of a vera causa. My answer to this is as 

 simple as even Dr. Le Conte can require : I did take account of 

 this vera causa in my investigations. But Dr. Le Conte will 

 answer, " You have said nothing about taking it into account in 

 your investigations." True, I said nothing about it, but I took 

 it into account for all that. How ? Let me explain. The vera 

 causa amounts to this — that the whole quantity of heat which 

 was distributed among a certain set of atmospheric particles 

 before the sound-wave reached them remains among the same 

 set of particles during the whole time of the wave's passage past 

 them. In other words, not any particle loses or gains heat (it 

 may lose or gain temperature) during its motion. Now heat is 

 the cause of the repulsive action among the particles, and is 



