62 Royal Society .-—Prof. Reynolds on 



according to our experience, have still possessed its full heat- 

 conducting power. This being supposed, it follows from the 

 dimensions of their apparatus, and from the emissive power 

 of glass, that the ratio of the quantities of heat carried over 

 by radiation and conduction in those experiments, for the tem- 

 perature 100° of the thermometer, was in one series of experi- 

 ments 6, and %\ in the other. Those experiments therefore 

 cannot be looked upon as rigorously demonstrating the law 

 founded upon them, the significance of which is moreover, ac- 

 cording to the authors themselves, detracted from by the depend- 

 ence of the specific heat of mercury on the temperature. 



X. Proceedings of Learned Societies. 



ROYAL SOCIETY. 



[Continued from vol. xlix. p. 478.] 



" AN the Refraction of Sound by the Atmosphere." By Professor 

 " Osborne Reynolds*. 



My object in this paper is to offer explanations of some of the 

 more "common phenomena of the transmission of sound, and to 

 describe the results of experiments in support of these explanations. 

 The first part of the paper is devoted to the action of ivind upon 

 sound. In this part of the subject I find that I have been preceded 

 by Professor Stokes, who in 1857 gave precisely the same expla- 

 nation as that which occurred to me. I have, however, succeeded 

 in placing the truth of this explanation upon an experimental basis ; 

 and this, together with the fact that my work upon this part of 

 the subject is the cause and foundation of what I have to say on 

 the second part, must be my excuse for introduciug it here. In 

 the second part of the subject I have dealt with the effect of the 

 atmosphere to refract sound upwards, an effect which is due to the 

 variation of temperature, and which I believe has not hitherto 

 been noticed. I have been able to show that this refraction ex- 

 plains the well-known difference which exists in the distinctness 

 of sounds by day and by night, as well as other differences in the 

 transmission of sound arising out of circumstances such as tem- 

 perature ; and I have applied it in particular to explain the very 

 definite results obtained by Professor Tyndall in his experiments off 

 the South Foreland. 



The Effect of Wind upon Sound 

 is a matter of common observation. Cases have been known in 

 which, against a high wind, guns could not be heard at a distance of 

 550 yards f, although on a quiet day the same guns might be 

 heard from ten to twenty miles. And it is not only with high 

 winds that the effect upon sound is apparent ; every sportsman 

 knows how important it is to enter the field on the lee side even 



* Read April 23, 1874, f Proa Roy. Soc. 1874, p. 62. 



