Mr. Ivory on the Astronomical Refractions. 425 



Desormes, and to 1-3748 by those of MM. Gay Lussac and 

 Welter. 



It thus appears that there is a great connection between my 

 Theory and the speculations of Laplace upon the Gases *. 

 And this leads me to remark upon a point about which I am 

 much more deeply concerned than I am about the travesty 

 which the S. B. L. has taken the trouble to make of my la- 

 bours. It may be said that I have been directed in my re- 

 searches by the ideas of the eminent French philosopher. 

 I am exculpated from this charge as far as regards what 

 M. Poisson has written on this subject either in the Con. des 

 Terns for 1826, or in the Annates de Physique for August 1823, 

 by the dates. The first Memoir of Laplace on the attrac- 

 tion of the Gases, published in the Con. des Terns 1824, was 

 read to the Academy of Sciences 10th September 1821. 

 Now I have undeniable evidence that, at this date, I was in 

 possession of my Theory as far as regards the present ques- 

 tion. The proofs, gentlemen, are contained in your Journal for 

 May and June 1821. The formula in the Number for Mav- 

 is derived from the equations (A) ; that in the next Number 

 is obtained by a particular transformation, taking the general 

 value m equal to 5 instead of 4. 



My theory has a broader foundation and embraces a greater 

 number of natural phenomena than the view of Laplace, 

 which is confined chiefly to the velocity of sound. Since 

 the equations are found to belong to an atmosphere different 

 m some respects from that of nature, we must infer that they 

 are approximate only, not rigorously true. All the reason- 

 ings and experiments seem to bear upon the first term of the 

 development of a function, not upon its complete expression. 

 It is this term only which is ascertained. The equations, as 

 far as they are yet known to us, may be thus expressed, 

 & _ i ' 



1 -f /3t' — 3 X 



f*(>^«(«-r5?)-(i— )0-'5) 



It is extremely probable that my numbers are the true values 

 of the indices; and that the experimental quantities are dif- 

 ferent only on account of the unavoidable errors attending 

 very delicate measurements. But I cannot now enter upon 

 any discussion of principles, and must confine myself to the 

 statement of results. Two consequences follow from the un- 

 expected coincidence of my Theory with the researches of 

 Laplace on the constitution of the Gases. First, we have a 

 direct and undeniable proof that Dal ton's law actually takes 

 * Mi-ran. Celeste, Li v. J2. 

 Vol. 63. No. 81 4. June 1824. SH place 



