A480 REPORT—1862. 
From 15,000 to 20,000 feet the temperature of the dew-point as deter- 
mined by 
Dry and Wet (free) Experiments, 
Was 1°1 higher than as found by Dry and Wet (aspirated) ..from 7 
gy O85 > a a Daniell’s Hygrometer .... ,, 9 
9 
Sot D 53 = 39 Regnault’s 95 Seer Aas 
Dry and Wet (aspirated) 
Was 0°-6 lower than as found by Daniell’s Hygrometer...... g378 AG 
ae Repnault’s) ~y35.- tte sana api le 
2 0 9 3) 9 2) 
Daniell’s Hygrometer 
Was 0-4 higher than as found by Regnault’s Hygrometer.... ,, 8 
By taking the mean of all, according to the number of experiments, we 
haye :— 
From the ground to 20,000 feet the mean temperature of the dew-point 
as found by 
Dry and Wet (free) 
Was 0°-2 higher than as found by Dry and Wet (aspirated) ..from 15 
5, 90° by ms - Daniell’s Hygrometer .... ,, 114 
tae, ae 5 iy ss Regnault’s =5 vcakebyne ced 
Dry and Wet (aspirated) 
Was 0° 9 higher than as found by Daniell’s Hygrometer .... ,, 10 
3, 0°6 lower 4 ee Regnault’s si its Sib an, cae 
Daniell’s Hygrometer 
Was 0°1 lower than as found by Regnault’s Hygrometer .. ,, 16 
From all the results it would seem that the temperature of the dew-point 
as deduced from the Dry- and Wet-bulb thermometers as ordinarily used has 
a tendency to give a result a little too high, but to an amount that is less than 
the probable error of observations, and that, therefore, it is a perfectly trust- 
worthy instrument to use, even to great altitudes; also, the results by 
Daniell’s Hygrometer seem to be of equal value with those found by Reg- 
nault’s Hygrometer, at all elevations. 
§ 8. Comparison oF THE READINGS OF THE MERCURIAL AND ANEROID 
BaROMETERS AT DIFFERENT HEIcuts, 
All the simultaneous readings of the Siphon and Aneroid Barometers were 
extracted from Table I. and inserted in the following Table. 
