Himalayan Journals, vol 2 by J. D. Hooker (great reads TXT) 📖

immediately before the ground became covered with snow for the remainder of the winter; during the three succeeding months,

therefore, the temperature of the soil probably does not fall below that of the snow, whilst the mean temperature of the air in January may be estimated at about 20 degrees, February 22 degrees, March 30

degrees, and April 35 degrees. If, again, we assume the temperature of the soil of Jongri to be that of other Sikkim localities between 10,000 and 14,000 feet, we may assume the soil to be warmer by 10

degrees in July (see Tungu observations), by 8 degrees or 9 degrees in September (see Yeumtong); by l0 degrees in October (see Tungu);

and by 7 degrees to l0 degrees in November (see Wallanchoon and

Nanki). These temperatures, however, vary extremely according to

exposure and amount of sunshine; and I should expect that the

greatest differences would be found in the sunny climate of Tibet,

where the sun's heat is most powerful. Were nocturnal or terrestrial radiation as constant and powerful as solar, the effects of the

latter would be neutralised; but such is not the case at any

elevation in Sikkim.

This accumulated heat in the upper strata of soil must have a very

powerful effect upon vegetation, preventing the delicate rootlets of shrubs from becoming frozen, and preserving vitality in the more

fleshy, roots, such as those of the large rhubarbs and small orchids, whose spongy cellular tissues would no doubt be ruptured by severe

frosts. To the burrowing rodents, the hares, marmots, and rats, which abound at 15,000 to 17,000 feet in Tibet, this phenomenon is even

more conspicuously important; for were the soil in winter to acquire the mean temperature of the air, it would take very long to heat

after the melting of the snow, and indeed the latter phenomenon would be greatly retarded. The rapid development of vegetation after the

disappearance of the snow, is no doubt also proximately due to the

heat of the soil, quite as much as to the increased strength of the sun's direct rays in lofty regions.

I have given in the column following that containing the temperature of the sunk thermometer, first the extreme temperatures of the air

recorded during the time the instrument was sunk; and in the next

following, the mean temperature of the air during the same period, so far as I could ascertain it from my own observations.

SERIES I.--Soane Valley

Locality Muddunpore

Date Feb. 11 to 12

Elevation 440 feet

Depth 3 ft. 4 in.

Temp. of sunk Therm. 71.5

Extreme Temperature of Air observed 62.0 to 77.5

Approximate Mean Temp. of Air deduced 67.0

Diff. between Air and sunk Therm. +4.5

Locality Nourunga

Date Feb. 12 to 13

Elevation 340 feet

Depth 3 ft. 8 in.

Temp. of sunk Therm. 71.7

Extreme Temperature of Air observed 57.0 to 71.5

Approximate Mean Temp. of Air deduced 67.3

Diff. between Air and sunk Therm. 3.4

Locality Baroon

Date Feb. 13 to 14

Elevation 345 feet

Depth 2 ft. 4 in.

Temp. of sunk Therm. 68.5

Extreme Temperature of Air observed 53.5 to 76.0

Approximate Mean Temp. of Air deduced 67.6

Diff. between Air and sunk Therm. 1.9

Locality Tilotho

Date Feb. 15 to 16

Elevation 395 feet

Depth 4 ft. 6 in.

Temp. of sunk Therm. 76.5

Extreme Temperature of Air observed 58.5 to 80.0

Approximate Mean Temp. of Air deduced 67.8

Diff. between Air and sunk Therm. 8.7

Locality Akbarpore

Date Feb. 17 to 19

Elevation 400 feet

Depth (2 therm.) 4 ft. 6 in.

5 ft. 6 in.

Temp. of sunk Therm. 76.0

Extreme Temperature of Air observed 56.9 to 79.5

Approximate Mean Temp. of Air deduced 68.0

Diff. between Air and sunk Therm. 8.0

SERIES II.--Himalaya of East Nepal and Sikkim.

Locality Base of Tonglo

Date May 19

Elevation 3,000 feet

Depth 2 ft. 0 in.

Temp. of sunk Therm. 78.0

Extreme Temperature of Air observed 67.5 to 67.0

Approximate Mean Temp. of Air deduced

Diff. between Air and sunk Therm.

Locality Simsibong

Date May 20

Elevation 7,000 feet

Depth 2 ft. 0 in.

Temp. of sunk Therm. 61.7

Extreme Temperature of Air observed 59.0 to 59.5

Approximate Mean Temp. of Air deduced

Diff. between Air and sunk Therm.

Locality Tonglo saddle

Date May 21 to 22

Elevation 10,008 feet

Depth 2 ft. 6 in.

Temp. of sunk Therm. 50.7*

Extreme Temperature of Air observed 47.5 to 57.5

Approximate Mean Temp. of Air deduced 52.5

Diff. between Air and sunk Therm.