1 8 Mr. Holmes on 



Ordinary Meeting, November 29th, 1887. 



Professor BALFOUR Stewart, LL.D., F.R.S., President 

 in the Chair. 



The President alluded to the paper on the derivation 

 of the heavenly bodies from meteorites, recently read by 

 Mr. Norman Lockyer before the Royal Society, and spoke 

 of it as likely to prove a useful working hypothesis. A brief 

 discussion ensued. 



The effect of the small variation of the density of the 

 atmosphere on the amplitude of plane waves of 

 Sound approaching the earth. By Ralph Holmes, 

 B.A. 



In considering the motion of plane waves of sound 

 through a medium of slowly varying density, supposing 

 that no considerable alteration of density occurs within a 

 distance of a great many wave lengths, it is customary to 

 neglect all considerations of a reflected wave at any part of 

 its course, and so to assume that the energy of the motion 

 must remain unchanged. From this hypothesis we may 

 deduce that the amplitude of vrbration varies inversely as 

 the square root of the density. Since, however, there is 

 a reflected wave at every part of its course, it has appeared 

 to me advisable to obtain an approximate value for its 

 amplitude, and to compare its value with that of the pro- 

 gressive wave that we may obtain some more definite idea 

 of the quantity we are neglecting. In the following paper 



