326 Mr. Addison's Remarks on the Itifluence of Terrestrial 



from a small condensation y. The equation may therefore 



be thus written, -- = &— 1 ; and as it is true of any number 



of continuous variations of density or volume, the pressure 

 being constant, it agrees with the equation (a) investigated 



above. Observing also that y = — , and k — 1 = ~, his 



two equations (5) and (6) will become, 



adr d(> 



\ + u6 ~" ~' 

 fidi _ d{ 



T+7T - "P 

 being the actual temperature of the air. In the first of these 

 equations, dy is derived from dr; and in the second, dg de- 

 termines di. The two equations are therefore intimately con- 

 nected, and no just conclusion can be deduced from the se- 

 cond, if the first be overlooked. Now M. Poisson has inte- 

 grated the second equation apart, and as if it were in no re- 

 spect modified by the first. This is the ground of my objec- 

 tion. In reality the integral he obtains satisfies the second 

 equation, but it does not satisfy the first, as it ought to do 

 according to his own calculations. If we reason fairly, and 

 fulfil all the relations of the differential quantities, we shall be 

 necessarily led, even when we follow M. Poisson's train of in- 

 vestigation, to the same theory explained in the present and 

 in former articles of this Journal*. 

 Oct. 13, 1828. J. Ivory. 



LV. Remarks on the Influence of Terrestrial Radiation in 

 determining the Site of Malaria. By Wm. Addison. 



[Concluded from p. 278.] 



ONE of the chief arguments in favour of the important in- 

 fluence exerted by terrestrial radiation in the production 

 of that state of the atmosphere favourable to the attacks of 

 disease, and known by the name of malaria, is drawn from 

 the fact that in almost, nay I might say every case, where the 

 violence of the symptoms induced by it will permit us to ob- 

 serve the first impressions which it causes, we find that its 

 baneful influence is exerted during the night-season, while in 

 the day-time it is comparatively, if not quite, inert. It would 

 be needless to reiterate here the numerous proofs of this, dis- 

 tributed among the writings of those many accurate observers 

 who have been at the pains of noticing the habitudes of ma- 



• See Phil. Mag. and Annals for October 1827, pp. 245, 246, 247. 



laria. 



