AT KEW OBSERVATORY AND THEIR DISCUSSION. 



497 



The agreement between the mean results from the 12 aneroids and those deduced 

 from the single term 



a- 196 



is extremely close. 



There are naturally very considerable irregularities amongst the individual results 

 in the table, but, with the solitary exception already alluded to, the phenomena 

 observed at the different pressures are very similar. The aneroids were made mainly 

 by CASELLA and HICKS, but they varied in diameter from 2 to 4^ inches. 



52. Mr. WHYMPER'S data as to recovery, though less varied, are also of interest. 

 On his p. 30 he gives the original errors, the errors on return to the original 

 pressure, and those observed 1 day and 1 week later for 36 aneroids, exposed for one 

 week to pressures varying from 14 to 26 inches. In 12 instances the reading was 

 higher after a week's recovery than it was prior to the experiment. 



On his p. 31 Mr. WHYMPER repeats some of these data for 20 of the aneroids, 

 adding also the errors observed after only 1 hour's recovery. I have omitted one of 

 the 20 aneroids, No. 40, because after a week's recovery it read '29 inch higher than 

 prior to the experiment, the figures suggesting the occurrence of a large permanent 

 change of zero before the end of the first day's recovery. According to the figures on 

 p. 31 there was also a permanent rise of zero in three other aneroids, Nos. 42, 22, 

 and 23. In the last-mentioned case, however, this seems due to a misprint of 

 236 for '206 in one of the data, the latter figure appearing on p. 30. In the 

 case of Nos. 22 and 42 the final reading exceeded the original by so small an amount 

 it seemed best to retain the aneroids. This retention accounts for the minus sign in 

 the second entry of the last column of Table XLVIII. When more than one aneroid 

 was exposed to a given pressure, I give only the mean values of the ratios for the 

 group. In many cases the aneroids are the same as were dealt with in Table XL VII. 



TABLE XLVIII. Ratios of Deficiencies to Original Deficiency (data from 



Mr. WHYMPER'S pp. 30, 31). 



VOL. CXCT. A. 



3 S 



