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DR. C. CHEBE, EXPERIMENTS ON ANEROID BAROMETERS 



greater than in the two previous tables. As temperature was about 4 lower in the 

 experiments at the slower rate, its influence must have tended if anything to reduce 

 the apparent difference. 



As we should have anticipated a priori, the differences in Table XXXI. are greatest 

 in the case of the two aneroids Nos. 2 and 3, which showed the largest after-effect 

 phenomena. 



Taking both the Tables XIX. and XXXI. into consideration, we see that the fall of 

 temperature naturally experienced in mountain ascents, and the reduction in the rate 

 of change of pressure relative to that of the ordinary test, must occasionally neutralise 

 one another's effects ; but the consequences, however satisfactory, can hardly, I think, 

 be justly ascribed to design. Though the differences exhibited in Table XXXI. are 

 certainly quite appreciable, they are very much less than would naturally be antici- 

 pated from experiments in which pressure is reduced rapidly and then maintained 

 constant for a lengthened period. 



31. The influence of the previous rate of reduction of the pressure on the fall of 

 reading at the lowest point is hardly capable of being satisfactorily ascertained from 

 the earlier groups of experiments, because with a stoppage of only 1 minutes we 

 have to do with changes of reading so small relative to the probable error of observation 

 that a large number of experiments are required to give results of much value. In 

 the last group of experiments, Nos. 71 to 75, however, the stoppages were sufficiently 

 long to produce considerable falls of reading. To avoid decimals I have applied a 

 common large multiplier, and give the results in Table XXXII. 



TABLE XXXII. Fall of Heading at Lowest Pressure (21 inches). 



The agreement between the falls in 120 minutes in the one set of experiments and 

 in 1080 minutes (120 X 9) in the other is remarkably close. A comparison of the 

 falls at the three shorter intervals, 2, 5, and 10 minutes in the one case, and 18, 45, 



