AT KEW OBSERVATORY AND THEIR DISCUSSION. 



459 



In these tables each entry depends on only one experiment, so the agreement 

 with the law, " fall proportional to range," could hardly be better. 



In the interval between these experiments and those dealt with in Tables IX. and X., 

 aneroid No. 1 had broken down and been altered. The figures obtained from the 

 other three aneroids stand to one another in almost exactly the same proportion 

 as before. 



18. To show more clearly that the law of variation of the fall of reading with the 

 time was nearly if not exactly the same for all four aneroids, I have in the following 

 Table XIII. multiplied the figures actually found for Nos. 1, 2, and 4 by 6/5, 8/7 

 and 2 respectively. The results are the means of the several ranges included in 

 Tables XI. and XII., but the observations at all the time intervals are included. 



TABLE XIII. Quantity for Aneroid No. 3, same as in Table XII. ; for the others, 



multipliers are applied, as explained above. 



After trying some logarithmic functions, I found that the results in Table XIII. 

 were more in accordance with a formula of the type 



fall, under stationary pressure = Ct v (7), 



where t denotes time elapsed since the pressure became stationary, while C and q are 

 constants for a given previous rate of fall. C varies, of course, from aneroid to 

 aneroid, but to all appearance there was at least a clcse approach to equality in the 

 values of q for the above four aneroids. Accordingly, I took the mean of the results 

 from all the aneroids in Table XIII., and determined q by trial. Table XIV. com- 

 pares the mean thus found for the observed values with results calculated from the 

 formula 



constant X fall = (31'3) t' m (8). 



The corresponding mean results from the first 24 experiments, as given in 

 Tables IX. and X., are added. 



3 N 2 



