Determination of the Acceleration of Gravity for Tokio, Japan. 43 



the work equated to zero will give 



RT ■ v 3 -q c „ 



*~t*-*i l0g *ri-« Tfa+./SXt-s + zS)- * * W 

 These are two simultaneous equations for the roots of the 

 cubic and «r, which can only be solved by trial and error. 

 Guided by Andrews's table for C0 2 at 13°*1, a temperature 

 safely below the critical point, I have substituted for -ar in 

 equation (6) the values 49 and 50, obtaining respectively the 

 cubics (0 = 1000 r) :— 



f - 20-4 2 + 106 0-147 = 0, .... (8) 

 whose roots are approximately, 



u = -002263, -004914, -013223; 

 and 



(f> 3 -2O0 2 + lO40-144=O, (9) 



whose roots are approximately, 



r = -002241, -00506, -01271. 



From these values of v 1 and u s substituted in equation (7), the 

 pressures obtained are respectively 49'50 and 49*60. The 

 value 49*5 for tst was then tried in equation (6), and gave, 

 from equation (7), the pressure 49'3. 



These calculations show that Clausius's formula represents, 

 with as great accuracy as we can obtain at present, the whole 

 of the experimental results given by Andrews for carbonic acid. 

 It is highly probable that a similar formula -will be applicable to 

 other substances : but before regarding it as a general formula, 

 equally accurate experiments must be made upon other gases. 

 I intend to examine the results recently given by Ansdell, in 

 order to test further the applicability of the general formula. 



VI. On the Determination of the Acceleration of Gravity for 

 Tokio, Japan. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 



YOUR correspondent is, we presume, the Major Herschel 

 who recently in ' Nature ' commenced his review on 

 Colonel Clarke's ' Geodesy ' thus :— " It is well that there are 

 men brave enough with the pen as there are others brave with 



