132 Daniell on a new Hygrometer. 



The correction alluded to amounts to +0.1 inches. It 

 may also be remarked, that the calculated means do not 

 rigorously correspond with each other : this is in consequence 

 of the decimal calculations having been carried on further in 

 some instances than others ; and fractions, which it was neces- 

 sary to leave out of the shorter periods, have become appre- 

 ciable in the longer, the means of the latter having been taken 

 from the whole series of experiments, and not from the mean* 

 of the former. 



The use of the Table will be perhaps better imderstood 

 from the following comparison of the quarters. Beginning with 

 the three months, December, January, and February, it will 

 be observed, that the mean of the barometer during that 

 period was at its lowest, while its range was greatest. The 

 quantity and pressure of vapour least, and the variation also 

 least. The degree of dryness and rate of evaporation were 

 likewise both at their minimum. The quantity of rain nearly 

 the smallest. The temperature lowest, and the range of the 

 thermometer least. During the quarter comprising the three 

 months of June, July, and August, on the contrary,- the mean 

 of the barometer was at its highest, and its range was least,—*- 

 the quantity and pressure of the vapour was greatest, — the de- 

 gree of dryness greatest, — rate of evaporation greatest, — and 

 quantity of rain greatest. The mean temperature was also at 

 a maximum. It may farther be remarked, that the mean of 

 these two extreme quarters is nearly the mean in all respects 

 of the whole year. 



The intermediate quarters, March, April, and May, and 

 September, October, and November, vary respectively very 

 little from the annual mean. The autumn, however, is marked 

 by more vapour, more rain and a less degree of dryness than 

 the spring, and it is during this period that the range of the 

 thermometer is greatest. 



From the average of the whole year we find that the degree 

 of dryness in the afternoon exceeds that of ten o'clock in the 

 morning by 1^"^^ while the degree of dryness of the nightfalls 

 short of the same by 4°. The evaporation of morning, noony 



