486 



DR. C. CHREE, EXPKRIMENTS ON ANEROID BAROMETERS 



as a rule, considerably larger than the percentage gain throughout the higher part of 

 the range. The latter, however, is a substantial quantity except in the case of the 

 stoppage at 2 1 inches for an hour only. 



39. As pressure was raised above the point where it was stationary in the 

 descent, the influence on the difference of the descending and ascending readings 

 gradually diminished, and by the time atmospheric pressure was reached there was 

 in every case a close approach to the normal deficiency in the reading. In some 

 cases the deficiency was even below the normal. There is, however, ground for 

 believing that even after return to the atmospheric pressure the stoppage exercised 

 some influence. The evidence for this conclusion is contained in Table XL., which 

 shows the rate of recovery in cases in which there was, and in other cases in which 

 there was not, a subsidiary stoppage, in addition to the stoppage of an hour at the 

 lowest point, 15 inches. The results are means for the three aneroids Nos. 4, 7, and 8. 



TABLE XL. Ratio of Deficiency to Original Deficiency, D,/D . 



C4 



62 



The experiments are, of course, not numerous enough to justify exact numerical 

 deductions, but it seems quite clear that the recovery in the two last cases in the 

 table was decidedly slower than in the first case. 



40. In addition to the experiments already referred to, there were two of earlier 

 date, Nos. 45 and 46, in which there was a subsidiary stoppage, lasting 24 hours, 

 during the descent. In the one the stoppage occurred at 26, in the other at 24 inches. 

 In both, pressure was reduced to 21 inches, the stoppage there lasting only 10 minutes, 

 and the ascent was of the normal type. At points below the stoppage the differences 

 between the descending and ascending readings were very decidedly less than in the 

 case of the normal experiments Nos. 36 and 39 treated as standards. The effect was 

 considerably larger when the stoppage occurred at 24 than when it occurred at 

 26 inches. In neither case, however, was the recovery at the end of the experiment 

 noticeably slow. 



41. After our discussion of the effects of a stoppage during the reduction of 

 pressure, a brief reference will suffice to a variety of experiments, Nos. 29, 30, 31, 32, 

 40, 41, 42, 43, and 44, in which there was a prolonged subsidiary stoppage during 

 the ascent of pressure. In all, the lowest pressure was 21 inches, and the stoppage 

 there lasted 10 minutes. 



