366 Mr. J. Glaisher's Remarlcs on the Weather 



ascribes to the air of preventing the immediate escape of the 

 developed heat or cold be demonstrated. At present this pro- 

 perty is hypothetical. The argument contained in this com- 

 munication would rather point to the inference, that the de- 

 veloped heat or cold instantly passes off in a radiant form, 

 without producing any very appreciable alteration of the state 

 of temperature of the air where it is generated. 



The mathematical investigation of the velocity of sound 

 which I have now expounded, originated in an attempt to ex- 

 plain theoretically the polarization of light exclusively on 

 hydrodynamical principles, the aether being treated as a con- 

 tinuous medium, the pressure of which, as in air of given 

 temperature, varies in the same proportion as the density. 

 My views on this subject are contained in several recent com- 

 munications to the Cambridge Philosophical Society. In the 

 course of the inquiry I found that the velocity of pi'opagation 

 in such a medium was not the value a, as generally supposed, 

 but a certain greater quantity a -v/ 1 +/", and that the expla- 

 nation of the phainomena of polarization essentially depended 

 on this result. I', was clearly, therefore, important to obtain 

 a numerical value of « i^l -f/r which could be tested by actual 

 observation of the velocity of sound. This I consider that I 

 have now done, and that I have thus removed an objection 

 which otherwise might have been urged against the proposed 

 theory of the polarization of light. 



Cambridge Observatory, 

 April 18, 1849. 



LIII. Kemarks on the Weather during the Quarter ending 

 March 31, IS^Q. ^j/ James Glaisher, Esq., of the Royal 

 Observatory^ Greejmich *. 



THE meteorological returns for the past quarter furnished 

 to the Registrar-General and myself have been received 

 from thirty-four different places, whose returns have passed 

 the necessary examination. The observations generally indi- 

 cate a decided improvement, having been made for the most 

 part by experienced observers, who have generally paid more 

 attention to their instruments than hitherto. The results are 

 therefore found to be more accordant with each other than 

 any previously received. 



Till January 7 and after March 18, the temperature of the 

 air was below its average value; the mean amount of the 

 deficiency of daily temperature in the former period was 6°'9, 

 and in the latter it was 3°'7. 



* Communicated by the Author. 



