184 Mr. T. R. Edmonds on the Elastic Force of 



equations we get 



Ho Hi H2 Ht-i 



or 



com 



and, taking common logarithms of each side, 



Now taking, according to the second of the above two equa- 

 tions, the value of 77^-, we get, on substituting for i the num- 



Ht-i 

 bers 1, 2, 3, and / in succession, and taking 10 as the unit of 

 temperature, 



i 2 1 1 



Qi _ ^ _ / 37'6 + l-0 + -5 \"fe_ /39-l\~fe 



qi~ p~V37-6+i-o--5y Us-iy ' 



^° loff^ 







*-R 



Q2_ f 376 + 20 + '5 \ * = ^40-l\ 



Qi" 



/ 37b + 2U + '5 \ * _ / 4U'JA 

 U7-6-J-2-0--5; " \S9'lJ 



Q< g P, = / 37-6 + f + -5 \"t _ / 38-1 + A "* 



Q,_! , w P, U7-6+t--5j "V37-1+J . ' 

 10 &p 



On multiplying together the quantities on the same sides of 

 the equations, we have 



Qo Qi Qa "' Q*-i "' L38-1 X 39-1 x * * '37'1+U ' 

 or 



Q,_ /38'l + A ~l-_/ * \'h 



Q ~\ 38-1 / (, ^381; * 



Consequently, taking the common logarithm, 



com log Q* = com log Q — j com log (l + — ^V 



This is a formula by means of which A log P* may be ascertained 

 for any temperature, with considerable precision, when A log P 

 for any other temperature is previously known. 



Among other formulae it may be useful to mention the fol- 

 lowing : — 



