526 Prof. R. Threlfall and Mr. J. F. Adair. On the 



Class A the velocity seems to increase with the temperature, but no 

 such law was detected in the other classes. 



In order to reduce the observed velocities (when corrected for the 

 temperature of the fork) to a comparable state, they are reduced to 

 one temperature ; and in the absence of a rule for doing this it is 

 supposed that each velocity in Class A, &c, is expressible in the 

 form Y A + at, where Y A denotes the velocity at some temperature 

 between the extreme temperatures of the observations in Class A, 

 and t is the excess of the temperature of the observation above the 

 chosen temperature. For Class A the temperature chosen was the 

 mean of the temperatures of the observations ; this mean is ap- 

 proximately 17" 791° C. Hence arises the system of equations 



Y A -0191a 





167567 



V A -0\L91a 





165943 



Y A -0'291a 





157308 



V A -0791a 





157791 



Y A -0791a 





148804 



Y A + 0-709a 





180697 



Y A +O709a 





193839 



Y A +O209a 





197940 



Y A + O209a 





163439 



Y A + 0'209a 





197540 



Y A +O209a 





174601. 



If the method of least squares be considered applicable, the equations 

 for the probable values of Y A and a are (Stewart and Gee, vol. 1, 

 p. 274) : 



llV A -0-001a = 1905469. 



{ 



-(0'091)Y A + 2- 5891a = 66858. 



These give — 



Y A = 173227, a = 25890. 



This large value of a will be merely used in getting the probable 

 error of the mean, i.e., of the above value of Y A . If it has a physical 

 meaning it is very noteworthy. Substituting the value 25890 for a 

 in the foregoing equations there arise the values : — * 



Departure from mean. 



Y A = 172512 -715 



170888 -2339 



164842 -8385' 



178270 +5043 



169283 -3944 



