CHEMICAL AND PHYSICAL NOTES. 161 
necessary to provide the means of observing its temperature accu- 
rately. 
The aneroid barometer has been mentioned as having, in some 
respects, the same advantages as the hypsometer, and it might be 
thought that the aneroid can, on such excursions, replace both the 
mercurial barometer and the hypsometer. But this is not so. The 
aneroid is a spring balance, and its spring soon gets tired, so that, for 
instance, on an excursion in mountainous countries, it might, on 
arriving in the evening at the camping place, show a certain pressure 
of the atmosphere, and the next morning it might show a different 
pressure, even although the real pressure had not varied in the 
interval. If the temperature of boiling water varies in the same 
place, it is proof that the pressure of the atmosphere has varied. 
But although the aneroid cannot replace the hypsometer, it may 
with advantage be used in connection with it for determining local 
variations of height or of atmospheric pressure during one day. The 
night and morning comparisons with the hypsometer give its error 
and rate for that day. 
EXAMPLES OF RAPID VARIATIONS OF ATMOSPHERIC TEMPERATURE, 
ESPECIALLY DURING FOHN. 
The following pages contain the record of peripatetic meteoro- 
logical observations made at different times. They are reprinted 
from a paper* on this subject published in the Proceedings of the 
Royal Society in 1894. 
“The variation of the temperature of the air in the course of a 
day is a matter of familiar observation. It depends in the first 
instance on the relative positions of the locality and the sun. The 
temperature is generally highest a short time after the sun has 
attained its greatest altitude above the horizon, and it is lowest some 
time after it has attained its greatest depression below the horizon. 
Observations made at regular intervals over the twenty-four hours 
show a more or less regular rise of temperature during the early part 
of the day and a similar fall of temperature during the latter part of 
the day and the evening. When the interval between the observa- 
tions is diminished the regularity of the march of temperature. is 
found to diminish also, but the great variability of the temperature 
of the air is best shown by the curve drawn by a recording ther- 
* ©On Rapid Variations of Atmospheric Temperature, especially during Fohn, and 
the methods of observing them, by J. Y. Buchanan, F.R.8. Proc. R. S. (1894), vol. lvi. 
p. 108. 
M 
