446 WRITINGS OP JOSEPH HENRY. [1874 



of the waves of sound — due to a difference in velocity in the 

 upper and lower portions of the currents of air. We do not 

 say however that the transmission of sound in the atmos- 

 phere is fully investigated, or that the abnormal phenomena 

 which are said to have been observed in connection with 

 fog-signal stations have been fully explained. So far from 

 this, we freely admit that we are as yet in ignorance as to how 

 the hypothesis we have adopted is applicable to the critical 

 explanation of the obstruction to soun^ in the abnormal 

 cases mentioned by General Duane. We feel however con- 

 siderable confidence in its power to afford a rational expla- 

 nation of these phenomena when the conditions under which 

 they exist shall have been accurately determined. 



We are further confirmed in our conclusion by the publi- 

 cation of an interesting paper in the Proceedings of the Royal 

 Society, by Professor Osborne Reynolds, of Owens College, 

 Manchester, intended to show that sound is not absorbed by 

 the condition of the atmosphere, but refracted in a manner 

 analogous to the hypothesis which has been adopted in the 

 preceding report. 



Much further investigation is required to enable us to 

 fully understand the effects of winds on the obstruction of 

 sound, and to determine the measure of the effect of varia- 

 tions of density in the air due to inequality of heat and 

 moisture. But such investigations can be made only under 

 peculiar conditions of weather and in favorable localities, 

 with the aid of a number of steamers, and a series of observ- 

 ers, by whom the transmissibility of sound may be simulta- 

 neously observed in different directions. The position which 

 we were so fortunate to obtain in our experiments in the lower 

 bay of New York at the season of the prevalence of land and 

 sea breezes was exceptionally favorable for the study of the 

 action of wind upon sound. It is the intention of the Light- 

 House Board to continue observations in regard to this 

 matter, and to embrace every favorable opportunity for their 

 prosecution under new and varied conditions. 



