248 MM. Jamin and Richard on the Cooling of Gases. 



making with the axis of the abscissse an angle whose tangent is 

 — 0*66, w^hich signifies that the exponent d' — c' is =0*66, or 



that c'=0'54. The columns No. 2 indicate the values of — z- 



ax 



derived from the right lines of the second system, opposite the 

 observed values; and it can be seen that they are equal to them. 

 This happy method has therefore permitted us to verify sepa- 

 rately the law relating to the two variables H and h, and to 

 determine the two exponents c' and d^. The coefficient m is 

 deduced from formula (3) : 



m = 



dh W 



dx hd' 



As many values are found as there have been observations ; and 

 the complete equality of all the results is a wholesale verification 

 of the formula found. 



n^ 

 Value of ??i= — j;' 



h. 



200 

 190 

 180 

 170 

 160 

 150 

 140 

 130 



Hydrogen (pressure 6897 millims.). 



n'. 



2-64 

 2-70 

 2-70 

 2-65 

 2-66 

 2-67 

 2-68 

 2-69 



h, 



120 . 



. . 2-70 



no . 



. 2-71 



100 . 



. 2-73 



90 . 



. . 2-71 



80 . 



. 2-73 



70 . 



. 2-72 



60 . 



. 2-71 



Mean 



2-69 



Formula (3) gives, for the velocity of diminution of pressure 

 of heated hydrogen, 



fJh ??' 



dx ctP^ 



(3) 



Such is the final formula, which sums up all the observations. 

 There only remained the extension of it to other gases, which 

 Me did for carbonic acid and air, the following being the numbers 

 found : — 



Carbonic acid. Air. 

 . 0-732 1-15 



0-.54 

 1-15 



0-54 

 1-13 



Hydrogen. 



2-695 



0-54 

 1-20 



Mean. 



0-54 

 1-16 



