AT KEW OBSERVATORY AND THEIR DISCUSSION.. 



483 



earlier experiments, Nos. 60 and 61, made respectively on August 17 and 20, 1897. 

 Of these 60 agreed in type with 63 and 66, while 61 was identical with 62 and 67. 

 Taking the means of the observed falls in reading during stated intervals of exposure 

 to 15 inches pressure in experiments 60, 63 and 66 as standards, I have found the 

 ratios borne to these by the corresponding mean falls in the other groups of experi- 

 ments during both the subsidiary stoppage and the stoppage at 15 inches. The 

 results appear in Table XXXVIII. The other data in the table are of the following 

 character : 



"Mean ratio" signifies the mean deduced from the values at the seven intervals 

 5, 10 ... 60 minutes. " Theoretical ratio " is what the value should have been accord- 

 ing to the law that the creep in a given interval of time is proportional to the 

 pressure interval measured from 30 inches. For instance, in experiments 64 and 65 

 the reading during the subsidiary stoppage at 21 inches should according to the law 

 have fallen (30-21) -~ (30-15), or '60, times as much in any given interval as it 

 did in the same interval during exposure to the pressure of 15 inches in experiments 

 60, 63 and 66. In reality the fall in the former case was on the average only '58 of 

 that in the latter. Accordingly the presumption is that the tendency to creep in 

 experiments 64 and 65 was less than in the three standard experiments in the 

 ratio 58 : 60. This result is utilised in calculating the true influence of the stoppage 

 at 21 inches on the fall of reading during the subsequent stoppage at 15 inches. 

 According to the actual observation figures the mean ratio of the falls at 1 5 inches in 

 experiments 64 and 65 to the falls in the standard experiments was '93, but on the 

 assumption that this suffered from the same cause as the creep at 21 inches, it should 

 be multiplied by 60/5B, in order to eliminate the difference between the aneroids' 

 mean state during the two groups of experiments. The result of this multiplication 

 is termed the " Corrected ratio." 



TABLE XXXVIIL- 



-Eatios to Falls of Reading (in same intervals) at 15 inches 

 in Standard Normal Experiments. 



3 Q 2 



