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334
THE ATMOSPHERE AND METEOROLOGY.
ference between the heat of summer and cold of winter is very great, it is
relatively very low in the ground that we must search for the point where
all the annual variations are neutralized. On the other hand, in those
countries where the temperature of the various seasons hardly differs, it
is only about a foot from the surface that the equalization of the annual
temperature is established. M. Boussingault has ascertained that, in order to know the annual temperature of New Granada and Ecuador, it is
sufficient in certain places to introduce the thermometer from one and a
half to two feet into the ground. Under the polar climates, where the
mean temperature of the atmosphere is below freezing-point, the few observations that have been made seem also to establish the fa^ct that the
zone of neutralization of exterior influences is nearer the surface than under temperate climates: in certain parts of New Britain it is said to have
a depth of only nine to fifteen feet.* At Yakutsk, where the thermomet-
ric average is twelve degrees Fahrenheit, the same temperature is found
at less than forty-eight feet; below this the ground becomes less cold,
owing to the internal heat of the earth; and toward three hundred and
ninety feet the sounding instruments finally arrive at layers of earth which
are not frozen.
Springs, like the soil, often show the average temperature of a country,
owing to their source in the cavities of the rocks. Indeed, by placing a
thermometer in the basins of springs, travelers can ascertain the average
climate of the regions through which they pass. Observations of this
kind are of great use, but they can not replace long and patient study of
atmospheric heat, One spring is, on an average, colder than the surrounding air, because its waters are produced by the melting of snows, or arise
from rains that fell on the slopes of high mountains; another spring,
slightly thermal, has traversed deep channels, where its temperature is
raised by the telluric heat; another has passed through fissures which are
chilled or warmed by currents of air circulating in the caverns of the
mountains. The slight
alternations of heat and
cold occurring in springs
are analogous to those
observed in the waters
of rivers. Water-courses,
always cooler in summer
and warmer in winter,
have a temperature all
the more equal the greater their velocity, because
they are subject during
less time to the changing atmospheric influences. Thus at Lyons, above
the confluence of the two rivers, the fluctuations of temperature during
various months of the year are seven degrees less in the furious Rhone
than in the peaceful Saone.
* Studer, Physikalische Geographie und Geologic, t. ii.
30°
c*»
20°J
£"
***o
Kn
\«
V,
lOpi
**"**"i
1^
'*Jr
\~?
J. F. Jt. A. M. J. J. JL S. O. "ff. J> J.
Fig. 150—Ordinary Temperatures of the Sa6ne and the Rhone
at Lyons.
| Title | The ocean, atmosphere, and life |
| Creator | Reclus, Elisée |
| Publisher | Harper |
| Place of Publication | New York |
| Date | 1873 |
| Language | eng |
| Type | Books/Pamphlets |
| Title | 00000367 |
| Type | Books/Pamphlets |
| Transcript | 334 THE ATMOSPHERE AND METEOROLOGY. ference between the heat of summer and cold of winter is very great, it is relatively very low in the ground that we must search for the point where all the annual variations are neutralized. On the other hand, in those countries where the temperature of the various seasons hardly differs, it is only about a foot from the surface that the equalization of the annual temperature is established. M. Boussingault has ascertained that, in order to know the annual temperature of New Granada and Ecuador, it is sufficient in certain places to introduce the thermometer from one and a half to two feet into the ground. Under the polar climates, where the mean temperature of the atmosphere is below freezing-point, the few observations that have been made seem also to establish the fa^ct that the zone of neutralization of exterior influences is nearer the surface than under temperate climates: in certain parts of New Britain it is said to have a depth of only nine to fifteen feet.* At Yakutsk, where the thermomet- ric average is twelve degrees Fahrenheit, the same temperature is found at less than forty-eight feet; below this the ground becomes less cold, owing to the internal heat of the earth; and toward three hundred and ninety feet the sounding instruments finally arrive at layers of earth which are not frozen. Springs, like the soil, often show the average temperature of a country, owing to their source in the cavities of the rocks. Indeed, by placing a thermometer in the basins of springs, travelers can ascertain the average climate of the regions through which they pass. Observations of this kind are of great use, but they can not replace long and patient study of atmospheric heat, One spring is, on an average, colder than the surrounding air, because its waters are produced by the melting of snows, or arise from rains that fell on the slopes of high mountains; another spring, slightly thermal, has traversed deep channels, where its temperature is raised by the telluric heat; another has passed through fissures which are chilled or warmed by currents of air circulating in the caverns of the mountains. The slight alternations of heat and cold occurring in springs are analogous to those observed in the waters of rivers. Water-courses, always cooler in summer and warmer in winter, have a temperature all the more equal the greater their velocity, because they are subject during less time to the changing atmospheric influences. Thus at Lyons, above the confluence of the two rivers, the fluctuations of temperature during various months of the year are seven degrees less in the furious Rhone than in the peaceful Saone. * Studer, Physikalische Geographie und Geologic, t. ii. 30° c*» 20°J £" ***o Kn \« V, lOpi **"**"i 1^ '*Jr \~? J. F. Jt. A. M. J. J. JL S. O. "ff. J> J. Fig. 150—Ordinary Temperatures of the Sa6ne and the Rhone at Lyons. |
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