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Himalayan Journals or Notes of A Naturalist Index      Next Appendix JK

 

Appendix


G. Part 2

 

[ 436 ]

 

ELEVATION 12,000 TO 13,000 FEET

 

EAST NEPAL AND SIKKIM CALCUTTA
No.
of
Obs.
Locality Elev. Month Temp. Dew
Point
Diff. Tens. Temp. Dew
Point
Diff. Tens.
  9
  9
  7
  7
  7
  8
  2
  1
  3
  7
  5
  1
  1
  6
  3
  4
  4
  4
  4
  6
23
13
  6
Zemu river, 7 a.m.
Zemu river, 9.50 a.m.
Zemu river, noon
Zemu river, 2.40 p.m.
Zemu river, 4 p.m.
Zemu river, sunset
Tangma Valley
Zemu river
Chumanako
Tungu, 7 a.m.
Tungu, 9.50 a.m.
Tungu, noon
Tungu, 2.40 p.m.
Tungu, sunset
Tungu, sunrise
Tungu, 9.50 a.m.
Tungu, noon
Tungu, 2.40 p.m.
Tungu, 4 p.m.
Tungu, sunset
Tungu, Miscellaneous
Tungu, Miscellaneous
Tuquoroma
12,070
12,070
12,070
12,070
12,070
12,070
12,129
12,422
12,590
12,751
12,751
12,751
12,751
12,751
12,751
12,751
12,751
12,751
12,751
12,751
12,751
12,751
12,994
|
| June
| and
| July
|
|
Nov.
June
Nov.
July
July
July
July
July
Oct.
Oct.
Oct.
Oct.
Oct.
Oct.
Oct.
July
Nov.
46·6
51·1
51·1
51·2
49·7
48·1
34·8
49·0
37·3
45·1
53·1
62·3
60·0
46·4
38·2
46·5
46·1
43·8
42·3
41·0
43·2
51·3
26·0
45·6
49·0
50·2
50·3
48·9
47·6
22·7
46·6
28·3
44·1
48·6
52·7
53·8
45·3
35·0
42·8
42·0
42·1
40·8
38·7
40·8
47·7
23·4
1·0
2·1
0·9
0·9
0·8
0·5
12·1  
2·4
9·0
1·0
4·5
9·6
6·2
1·1
3·2
3·7
4·1
1·7
1·5
2·3
2·4
3·6
2·6
·321
·362
·376
·377
·360
·344
·143
·332
·174
·305
·355
·409
·425
·317
·222
·292
·284
·285
·271
·253
·272
·345
·146
80·6
84·5
87·0
86·3
86·5
81·4
70·6
93·2
75·1
80·5
87·1
88·9
85·3
84·7
79·4
85·0
85·0
86·4
85·9
83·3
84·5
85·7
75·1
77·7
75·1
82·2
80·0
80·2
77·5
63·7
79·6
73·8
78·3
79·4
77·8
79·5
79·1
77·8
78·6
78·2
78·8
78·5
78·2
78·4
79·0
60·8
2·9
9·4
4·8
6·3
6·3
3·9
6·9
13·6  
1·3
2·2
7·7
11·1  
5·8
5·6
1·6
6·4
6·8
7·6
7·4
5·1
6·1
6·7
14·3  
·931
·972
1·074  
1·000  
1·006  
·926
·592
·989
·822
·949
·982
·935
·985
·974
·932
·957
·944
·963
·956
·947
·950
·971
·537
140       Mean 46·3 42·9 3·4 ·303 83·6 77·1 6·5 ·926
  East Nepal
and Sikkim
Calcutta
Humidity
Weight of vapour
0·890
3·37 gr.
0·815
9·75 gr.

 

ELEVATION 13,000 TO 14,000 FEET

 

EAST NEPAL AND SIKKIM CALCUTTA
No.
of
Obs.
Locality Elev. Month Temp. Dew
Point
Diff. Tens. Temp. Dew
Point
Diff. Tens.
  7
  4
  2
21
  1
  4
10
  1
  3
Mon Lepcha
Mon Lepcha
Tunkra valley
Jongri
Zemu river
Choonjerma
Yangma village
Wallanchoon road
Kambachen, below pass
13,090
13,073
13,111
13,194
13,281
13,288
13,502
13,505
13,600
Jan.
Jan.
Aug.
Jan.
June
Dec.
Nov./Dec.
Nov.
Dec.
27·1
25·6
45·0
22·7
46·7
39·0
33·8
28·0
40·0
18·5
16·4
43·5
10·5
46·7
11·1
18·6
  9·5
18·6
  8·6
  9·2
  1·5
12·2
0
27·9
15·2
18·5
21·4
·122
·113
·298
·091
·334
·093
·123
·088
·123
70·0
71·7
81·2
70·6
92·9
69·8
78·9
66·4
72·9
50·8
49·4
78·7
53·2
86·6
61·8
62·1
61·8
62·2
19·2
21·8
  2·5
17·4
  6·2
  8·0
16·8
  4·6
10·7
·527
·373
·962
·417
1·230  
·555
·561
·555
·563
53     Mean 34·2 21·5 12·6 ·154 74·9 63·0 11·9 ·636
  East Nepal
and Sikkim
Calcutta
Humidity
Weight of vapour
0·634
1·61 gr.
0·678
6·28 gr.

 

[ 437 ]

 

ELEVATION 15,000 TO 16,000 FEET

 

EAST NEPAL AND SIKKIM CALCUTTA
No.
of
Obs.
Locality Elev. Month Temp. Dew
Point
Diff. Tens. Temp. Dew
Point
Diff. Tens.
  1
  1
  8
12
  6
  4
  8
10
16
  8
  6
  3
  2
  1
  1
Yangma valley
Choonjerma pass
Lachee-pia
Momay, 7 a.m.
Momay, 9.50 a.m.
Momay, noon
Momay, 2.40 p.m.
Momay, 4 p.m.
Momay, sunset
Momay, Miscellaneous
Momay, Miscellaneous
Sittong
Palung
Kambachen pass
Yeumtong
15,186
15,259
15,262
15,262
15,262
15,262
15,262
15,262
15,262
15,262
15,262
15,372
15,676
15,770
15,985
Dec.
Dec.
Aug.
Sept.
Sept.
Sept.
Sept.
Sept.
Sept.
Sept.
Oct.
Oct.
Oct.
Dec.
Sept.
42·2
34·3
42·0
39·4
50·9
51·7
49·7
44·4
41·5
47·6
40·9
38·6
44·6
26·5
44·6
20·7
10·5
41·6
34·7
41·7
43·6
41·9
41·3
38·6
41·4
36·5
29·8
39·8
15·9
43·7
21·5
23·8
  0·4
  4·7
  9·2
  8·1
  7·8
  3·1
  2·9
  6·2
  4·4
  8·8
  4·8
10·6
  0·9
·133
·091
·279
·219
·280
·299
·283
·276
·252
·277
·234
·184
·262
·111
·300
80·8
77·9
85·5
80·5
87·6
89·5
90·0
88·7
84·2
87·4
83·9
84·0
86·8
78·0
88·8
 
62·0
60·6
79·4
78·8
78·8
79·7
78·3
77·6
78·4
78·6
69·3
77·5
78·5
58·5
80·5
18·8
17·3
  6·1
  1·7
  8·8
  9·8
11·7
11·1
  5·8
  8·8
14·6
  6·5
  8·3
19·5
  8·3
·559
·534
·982
·966
·963
·990
·949
·928
·952
·956
·710
·926
·954
·498
1·016  
87     Mean 42·6 34·8   7·8 ·232 84·9 74·4 10·5 ·859
  East Nepal
and Sikkim
Calcutta
Humidity
Weight of vapour
0·763
2·55 gr.
0·719
8·95 gr.

 

ELEVATION 16,000 TO 17,000 FEET

 

EAST NEPAL AND SIKKIM CALCUTTA
No.
of
Obs.
Locality Elev. Month Temp. Dew
Point
Diff. Tens. Temp. Dew
Point
Diff. Tens.
1
3
1
5
6
1
Kanglachem pass
Tunkra pass
Wallanchoon pass
Yeumtso
Cholamoo lake
Donkia mountain
16,038
16,083
16,756
16,808
16,900
16,978
Dec.
Aug.
Nov.
Oct.
Oct.
Sept.
32·8
39·8
18·0
32·4
31·4
40·2
16·3
38·7
–6·0
25·1
20·2
25·9
16·5
  1·1
24·0
  7·3
11·2
14·3
·110
·252
·046
·156
·130
·160
80·7
86·0
79·9
85·0
79·8
87·6
61·1
78·7
57·6
75·7
68·4
78·8
19·6
  7·3
22·3
  9·3
11·4
  8·8
·543
·959
·483
·872
·690
·963
17       Mean 32·4 20·0 12·4 ·142 83·2 70·1 13·3 ·752
  East Nepal
and Sikkim
Calcutta
Humidity
Weight of vapour
0·640
1·53 gr.
0·658
7·80 gr.

 

[ 438 ]

 

ELEVATION 17,000 TO 18,500 FEET

 

EAST NEPAL AND SIKKIM CALCUTTA
No.
of
Obs.
Locality Elev. Month Temp. Dew
Point
Diff. Tens. Temp. Dew
Point
Diff. Tens.
1
1
1
3
2
2
Kinchinjhow
Sebolah pass
Donkia mountain
Bhomtso
Donkia pass
Donkia pass
17,624
17,585
18,307
18,450
18,466
18,466
Sept.
Sept.
Sept.
Oct.
Sept.
Oct.
47·5
46·5
38·8
54·0
41·8
40·1
30·9
34·6
35·3
  4·4
30·3
25·0
16·6
11·9
  3·5
49·6
11·5
15·1
·191
·218
·224
·072
·188
·155
85·7
88·8
90·7
91·1
84·1
86·5
79·7
80·0
79·3
61·1
78·4
65·5
  6·0
  8·8
11·4
20·0
  5·7
21·0
·991
1·002  
·981
·543
·950
·627
10       Mean 44·8 26·8 18·0 ·175 87·8 74·0 12·2 ·849
  East Nepal
and Sikkim
Calcutta
Humidity
Weight of vapour
0·532
1·90 gr.
0·648
8·78 gr.

 

SUMMARY

 

HUMIDITY WEIGHT OF VAPOUR
No. of
Obs.
Elevations in
Feet
Stations Sikkim Calcutta Diff.
Sikkim
Sikkim Calcutta Diff.
Sikkim
  48
  49
  48
137
260
  76
1023  
193
  18
123
104
140
  53
  87
  17
  10
     735 to    2000
   2000 to    3000
   3000 to    4000
   4000 to    5000
   5000 to    6000
   6000 to    7000
   7000 to    8000
   8000 to    9000
   9000 to 10,000
10,000 to 11,000
11,000 to 12,000
12,000 to 13,000
13,000 to 14,000
15,000 to 16,000
16,000 to 17,000
17,000 to 18,000
  9
  9
13
23
15
13
14
13
  5
10
  6
  6
  9
  8
  6
  5
·717
·820
·858
·837
·865
·845
·826
·858
·747
·878
·860
·890
·634
·763
·640
·532
·663
·740
·732
·730
·730
·701
·668
·730
·724
·740
·760
·815
·678
·719
·658
·648
+·054  
·080
·116
·107
·135
·144
·158
·128
·023
·138
·100
·075
–·044  
+·044  
·018
–·116  
5·57
5·45
4·23
4·33
4·70
3·60
3·85
4·23
2·80
3·35
3·46
3·37
1·61
2·55
1·53
1·90
6·88
7·13
6·60
7·12
7·34
6·71
7·28
8·75
6·28
8·70
9·00
9·75
6·28
8·95
7·80
8·78
–1·31  
1·68
2·37
2·79
2·64
3·11
3·43
4·52
3·48
4·35
5·54
6·38
4·67
6·40
6·27
6·88
2386     154              

 

Considering how desultory the observations in Sikkim are, and how much affected by local circumstances, the above results must be considered highly satisfactory: they prove that the relative humidity of the atmospheric column remains pretty constant throughout all elevations, except when these are in a Tibetan climate; and when above 18,000 feet, elevations which I attained in fine weather only. Up to 12,000 feet this constant humidity is very marked; the observations made at greater elevations


 

[ 439 ]

 

were almost invariably to the north, or leeward of the great snowy peaks, and consequently in a drier climate; and there it will be seen that these proportions are occasionally inverted; and in Tibet itself a degree of relative dryness is encountered, such as is never equalled on the plains of Eastern Bengal or the Gangetic delta. Whether an isolated peak rising near Calcutta, to the elevation of 19,000 feet, would present similar results to the above, is not proven by these observations, but as the relative humidity is the same at all elevations on the outermost ranges of Sikkim, which attain 10,000 feet, and as these rise from the plains like steep islands out of the ocean, it may be presumed that the effects of elevation would be the same in both cases.

The first effect of this humid wind is to clothe Sikkim with forests, that make it moister still; and however difficult it is to separate cause from effect in such cases as those of the reciprocal action of humidity on vegetation, and vegetation on humidity, it is necessary for the observer to consider the one as the effect of the other. There is no doubt that but for the humidity of the region, the Sikkim Himalaya would not present the uniform clothing of forest that it does; and, on the other hand, that but for this vegetation, the relative humidity would not be so great.*

The great amount of relative humidity registered at 6000 to 8000

* Balloon ascents and observations on small mountainous islands, therefore, offer the best means of solving such questions: of these, the results of ballooning, under Mr. Welsh's intrepid and skilful pioneering (see Phil. Trans. for 1853), have proved most satisfactory; though, from the time for observation being short, and from the interference of belts of vapour, some anomalies have not been eliminated. Islands again are still more exposed to local influences, which may be easily eliminated in a long series of observations. I think that were two islands, as different in their physical characters as St. Helena and Ascension, selected for comparative observations, at various elevations, the laws that regulate the distribution of humidity in the upper regions might be deduced without difficulty. They are advantageous sites, from differing remarkably in their humidity. Owing partly to the indestructible nature of its component rock (a glassy basalt), the lower parts of Ascension have never yielded to the corroding effects of the moist sea air which surrounds it; which has decomposed the upper part into a deep bed of clay. Hence Ascension does not support a native tree, or even shrub, two feet high. St. Helena, on the other hand, which can hardly be considered more favourably situated for humidity, was clothed with a redundant vegetation when discovered, and trees and tree-ferns (types of humidity) still spread over its loftiest summits. Here the humidity, vegetation, and mineral and mechanical composition reciprocate their influences.


 

[ 440 ]

 

feet, arises from most of the observations having been made on the outer range, where the atmosphere is surcharged. The majority of those at 10,000 to 12,000 feet, which also give a disproportionate amount of humidity, were registered at the Zemu and Thlonok rivers, where the narrowness of the valleys, the proximity of great snowy peaks, and the rank luxuriance of the vegetation, all favour a humid atmosphere.

I would have added the relative rain-fall to the above, but this is so very local a phenomenon, and my observations were so repeatedly deranged by having to camp in forests, and by local obstacles of all kinds, that I have suppressed them; their general results I have given in Appendix F.

I here add a few observations, taken on the plains at the foot of the Sikkim Himalaya during the spring months.

 

Comparison between Temperature and Humidity of the Sikkim Terai and Calcutta, in March and April, 1849.

 

No.
of
Obs.
Locality Elev.
above
sea.
Feet
TEMPERATURE DEW POINT TENSION SAT.
C. T. C. T. C. T. C. T.
4
4
3
3
4
3
2
8
Rummai
Belakoba
Rangamally
Bhojepore
Thakyagunj
Bhatgong
Sahibgunj
Titalya
293
368
275
404
284
225
231
362
82·2
92·8
84·2
90·1
84·9
87·4
80·2
85·5
70·6
85·5
75·0
81·2
77·1
74·9
68·0
80·0
61·7
62·6
68·7
54·1
61·3
64·7
66·2
55·4
60·5
63·0
62·5
44·3
60·8
54·6
53·1
56·1
·553
·570
·695
·429
·547
·611
·642
·448
·532
·578
·568
·308
·537
·436
·414
·459
·517
·382
·605
·313
·466
·480
·635
·376
·717
·485
·665
·295
·588
·512
·409
·459
31   Means 305 85·9 79·0 61·8 56·9 ·562 ·479 ·472 ·516
  May, 1850
Kishengunj
131 89·7 K 78·6    76·7 K 71·4    ·904 K ·759    ·665 K ·793   
Vapour in a cubic foot
Kishengunj
Calcutta
8·20
9·52
Terai
Calcutta
5·08
5·90
Mean difference of temperature between Terai and Calcutta,
    from 31 observations in March, as above, excluding mimima,       Terai
Mean difference from 26 observations in March, including mimima, Terai
Mean difference of temperature at Siligoree on May 1, 1850
Mean difference of temperature at Kishengunj on May 1, 1850
6·9
9·7
10·9
11·1

 

From the above, it appears that during the spring months, and before the rains commence, the belt of sandy and grassy land along the Himalaya, though only 3·5° north of Calcutta, is at least 6° or 7° colder, and always more humid relatively, though there is absolutely less moisture suspended in the air. After the rains commence; I believe that this is in a great measure inverted, the plains becoming


 

[ 441 ]

 

excessively heated, and the temperature being higher than at Calcutta. This indeed follows from the well known fact that the summer heat increases greatly in advancing north-west from the Bay of Bengal to the trans-Sutledge regions; it is admirably expressed in the maps of Dove's great work "On the Distribution of Heat on the Surface of the Globe."

 




 
H.

ON THE TEMPERATURE OF THE SOIL AT VARIOUS ELEVATIONS.

 

These observations were taken by burying a brass tube two feet six inches to three feet deep, in exposed soil, and sinking in it, by a string or tied to a slip of wood, a thermometer whose bulb was well padded with wool: this, after a few hours' rest, indicates the temperature of the soil. Such a tube and thermometer I usually caused to be sunk wherever I halted, if even for one night, except during the height of the rains, which are so heavy that they communicate to the earth a temperature considerably above that of the air.

The results proved that the temperature of the soil at Dorjiling varies with that of the month, from 46° to 62·2°, but is hardly affected by the diurnal variation, except in extreme cases. In summer, throughout the rains, May to October, the temperature is that of the month, which is imparted by the rain to the depth of eleven feet during heavy continued falls (of six to twelve inches a day), on which occasions I have seen the buried thermometer indicating a temperature above the mean of the month. Again, in the winter months, December and January, it stands 5° above the monthly mean; in November and February 4° to 5°; in March a few degrees below the mean temperature of the month, and in October above it; April and May being sunny, it stands above their mean; June to September a little below the mean temperature of each respectively.

The temperature of the soil is affected by:—1. The exposure of the surface; 2. The nature of the soil; 3. Its permeability by rain, and the presence of underground springs; 4. The sun's declination; 5. The elevation above the sea, and consequently the heating power of the sun's rays: and 6, The amount of cloud and sunshine.

The appended observations, though taken at sixty-seven places, are


 

[ 442 ]

 

far from being sufficient to supply data for the exact estimation of the effects of the sun on the soil at any elevation or locality; they, however, indicate with tolerable certainty the main features of this phenomenon, and these are in entire conformity with more ample series obtained elsewhere. The result, which at first sight appears the most anomalous, is, that the mean temperature of the soil, at two or three feet depth, is almost throughout the year in India above that of the surrounding atmosphere. This has been also ascertained to be the case in England by several observers, and the carefully conducted observations of Mr. Robert Thompson at the Horticultural Society's Gardens at Chiswick, show that the temperature of the soil at that place is, on the mean of six years, at the depth of one foot, 1° above that of the air, and at two feet 1·5°. During the winter months the soil is considerably (l° to 3°) warmer than the air, and during summer the soil is a fraction of a degree cooler than the air.

In India, the sun's declination being greater, these effects are much exaggerated, the soil on the plains being in winter sometimes 9° hotter than the air; and at considerable elevations in the Himalaya very much more than that; in summer also, the temperature of the soil seldom falls below that of the air, except where copious rain-falls communicate a low temperature, or where forests interfere with the sun's rays.

At considerable elevations these effects are so greatly increased, that it is extremely probable that at certain localities the mean temperature of the soil may be even 10° warmer than that of the air; thus, at Jongri, elevation 13,194 feet, the soil in January was 34·5°, or 19·2° above the mean temperature of the month, 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°, February 22°, March 30°, and April 35°. 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° in July (see Tungu observations), by 8° or 9° in September (see Yeumtong); by l0° in October (see Tungu); and by 7° to l0° in November (see Wallanchoon and Nanki). These temperatures,


 

[ 443 ]

 

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 Date Eleva-
tion
(feet)
Depth
(ft. in.)
Temperature
of sunk
Thermometer
Extreme
Temperature
of Air
observed
Approx.
Mean
Temp.
of Air
deduced
Diff.
between
Air and
sunk
Therm.
Muddunpore
Nourunga
Baroon
Tilotho
 
Akbarpore
Feb. 11 to 12
Feb. 12 to 13
Feb. 13 to 14
Feb. 15 to 16
 
Feb. 17 to 19
440
340
345
395
 
400
3    4
3    8
2    4
4    6
(2 ther.)
4    6
5    6
71·5
71·7
68·5
76·5
 
76·0
62·0 to 77·5
57·0 to 71·0
53·5 to 76·0
58·5 to 80·0
 
56·9 to 79·5
67·0
67·3
67·6
67·8
 
68·0
+4·5  
3·4
1·9
8·7
 
8·0




 

[ 444 ]

 

SERIES II. Himalaya of East Nepal and Sikkim

 

Locality Date Eleva-
tion
(feet)
Depth
(ft. in.)
Temperature
of sunk
Thermometer
Extreme
Temperature
of Air
observed
Approx.
Mean
Temp.
of Air
deduced
Diff.
between
Air and
sunk
Therm.
Base of Tonglo
Simsibong
Tonglo saddle
Tonglo summit
Simonbong
Nanki
Sakkiazong
Mywa guola
Banks of Tambur
    higher up river
Wallanchoon
Yangma village
Yangma river
Bhomsong
Tchonpong
Jongri
Buckeem
Choongtam
Junction of
    Thlonok and Zemu
Tungu
Tungu
Lamteng
Choongtam
Lachoong
Yeumtong
Momay
Yeumtso
Lachoong
Great Rungeet
Leebong
Kursiong
Leebong
Punkabaree
 
 
 
 
 
Jillapahar
    (Mr. Hodgson’s)
 
 
 
 
 
Superintendent’s house
May 19
May 20
May 21 to 22
May 23
May 24
Nov. 4 to 5
Nov. 9 to 10
Nov. 17 to 18
Nov. 18 to 19
Nov. 19 to 20
Nov. 23 to 25
Nov. 30 to Dec. 3
Dec. 2 to 3
Dec. 24 to 25
Jan. 4
Jan. 10 to 11
Jan.12
May 19 to 25
 
June 13 to 16
July 26 to 30
Oct. 10 to 15
Aug. 1 to 3
Aug. 13 to 15
Aug. 17 to 19
Sept. 2 to 8
Sept. 10 to 14
Oct. 16 to 18
Oct. 24 to 25
Feb. 11 to 13
Feb. 14 to 15
Apr. 16
Apr. 22
May 1
| Aug. 15 to 16
| Aug. 15 to 16
| Aug. 20 to 22
| Aug. 20 to 22
| Sept. 9
| Sept. 9
| Oct. 6
| Oct. 20
| Feb. 18 to 28
| Mar. 1 to 13
| Apr. 18 to 20
| Apr. 30
Apr. 21 to 30
3,000
7,000
10,008
10,079
5,000
9,300
8,353
2,132
2,545
3,201
10,386
13,502
10,999
1,596
4,978
13,194
8,665
5,268
 
10,846
12,751
12,751
8,884
5,268
8,712
11,919
15,362
16,808
8,712
818
6,000
4,813
6,000
1,850
7,430
7,430
7,430
7,430
7,430
7,430
7,430
7,430
7,430
7,430
7,430
7,430
6,932
2    0
2    0
2    6
2    6
2    6
3    0
3    0
3    0
3    0
3    0
2    0
2    0
2    7
2    7
2    7
2    7
2    7
2    7
 
2    7
2    5
2    7
2    7
2    7
2    7
2    7
2    7
2    7
2    7
2    7
2    7
2    7
2    7
2    7
5    0
7    7
5    0
7    7
5    0
7    7
7    7
7    7
2    7
2    7
2    7
2    7
2    7
78
61·7
50·7*
49·7
69·7
51·5
53·2
73·0
71·0
64·5
43·5 to 45·0
37·3 to 38·0
41·4 to 42·0
64·5 to 65·0
55·0
34·5
43·2
62·5 to 62·7
 
51·2
59·0 to 56·5
50·8 to 52·5
62·2 to 62·5
72·1
66·3 to 66·0
55·5 to 56·1
52·5 to 51·5
43·5 to 43·0
60·2
65·0
50·8 to 52·0
64·5
61·8 to 62·0
80·0
62·0 to 62·8
61·5 to 62·3
61·6 to 61·7
60·7
60·2
60·5
60·0
58·5
46·0 to 46·7
46·3 to 48·3
55·3 to 56·0
57·4
58·8 to 60·2
67·5 to 67·0
59·0 to 59·5
47·5 to 57·5
47·5 to 53·2
51·2 to 55·5
33·0 to 50·5
37·8 to 55·0
41·0 to 85·0
48·0 to 65·0
44·3 to 60·0
25·0 to 49·7
20·0 to 46·0
23·0 to 40·0
42·8 to 71·3
33·0 to 54·8
  3·7 to 34·0
40·0 to 29·8
48·0 to 78·3
 
38·2 to 57·2
38·0 to 62·3
34·5 to 53·3
47·5 to 78·2
54·8 to 82·0
43·5 to 68·7
39·5 to 59·5
31·0 to 62·5
  4·0 to 52·0
39·0 to 62·6
56·0 to 71·0
41·5 to 56·0
63·0 to 60·0
54·0 to 67·8
68·2 to 78·0
58·0 to 66·0
58·0 to 66·0
58·7 to 67·8
58·7 to 67·8
56·2 to 65·0
56·2 to 65·0
52·0 to 61·0
49·7 to 55·2
36·0 to 52·8
34·5 to 53·3
46·0 to 61·3
46·0 to 61·3
48·5 to 65·8
 
 
52·5
52·5
52·5
41·2
46·1
63·4
55·6
51·6
37·4
33·0
27·9
57·1
43·9
15·3
32·4
63·2
 
49·8
50·0
41·1
57·0
72·0
57·0
47·2
41·6
30·6
52·0
63·5
46·0
63·0
60·0
76·0
61·5
61·5
61·7
61·7
60·0
60·0
58·5
56·5
43·0
46·0
54·0
55·0
58·0
 
 
–  1·8
–  1·8
–  1·8
+  9·7
+  7·1
+  9·6
+15·4
+12·9
+  7·6
+  4·7
+  3·6
+  6·6
+11·1
+19·2
+10·8
–  0·6
 
+  1·4
+  7·7
+10·7
+  5·3
+  0·1
+  9·2
+  8·6
+10·4
+12·6
+  8·2
+  1·5
+  5·4
+  1·5
+  1·9
+  4·0
+  0·9
+  0·4
–  0·1
–  1·0
+  0·2
+  0·5
+  1·5
+  2·0
+  6·4
+  1·3
+  1·7
+  2·4
+  1·5

* Sheltered by trees, ground spongy and wet.


 

[ 445 ]

 

SERIES III. Plains of Bengal

 

Locality Date Eleva-
tion
(feet)
Depth
(ft. in.)
Temperature
of sunk
Thermometer
Extreme
Temperature
of Air
observed
Approx.
Mean
Temp.
of Air
deduced
Diff.
between
Air and
sunk
Therm.
Kishengunj
Dulalgunj
Banks of Mahanuddy river
    Ditto
    Ditto
Maldah
Mahanuddy river
Ganges
Bauleah
Dacca
May 3 to 4
May 7
May 8
May 9
May 10
May 11
May 14
May 15
May 16 to 18
May 28 to 30
131
130
100
100
100
100
100
100
130
  72
2    7
2    7
2    7
2    7
2    7
2    7
2    7
2    7
2    7
2    7
§82·8 to 83·0
§81·3
†79·3
†87·5
†88·0
†88·8
†87·8
†88·0
  87·8 to 89·8
  84·0 to 84·3
70·0 to   85·7
74·3 to   90·3
75·0 to   91·5
77·8 to   92·5
78·5 to   91·5
75·3 to   91·3
71·0 to   91·7
73·0 to   87·8
78·0 to 106·5
75·3 to   95·5
82·0
82·0
83·0
83·0
82·3
82·3
82·3
82·3
80·5
83·3
+0·8
–0·7
–3·7
–4·5
–5·7
–6·5
–4·5
–5·7
+7·3
+0·9


 

SERIES IV. Khasia Mountains

 

Locality Date Eleva-
tion
(feet)
Depth
(ft. in.)
Temperature
of sunk
Thermometer
Extreme
Temperature
of Air
observed
Approx.
Mean
Temp.
of Air
deduced
Diff.
between
Air and
sunk
Therm.
Churra
Churra
Kala-panee
Kala-panee
Kala-panee
Kala-panee
Moflong
Moflong
Moflong
Syong
Syong
Myrung
Myrung
Myrung
Myrung
Nunklow
Nunklow
Pomrang
Pomrang
June 28 to 25
Oct. 29 to Nov. 16
June 28 to 29
Aug. 5 to 7
Sept. 13 to 14
Oct. 27 to 28
June 30 to July 4
July 30 to Aug. 4
Oct. 25 to 27
July 29 to 30
Oct. 11 to 12
July 9 to 10
July 26 to 29
Oct. 12 to 17
Oct. 21 to 25
July 11 to 26
Oct. 17 to 21
Sept. 15 to 23
Oct. 6 to 10
4,226
 
5,302
 
 
 
6,062
 
 
5,725
 
5,647
 
 
 
4,688
 
5,143
 
2    7
 
2    7
 
 
 
2    7
 
 
2    7
 
2    7
 
 
 
2    7
 
2    7
 
*71·8 to 72·3
  68·3 to 64·0
  69·2
  70·0 to 70·4
*70·2
*66·3
  65·0
  67·3
  63·2
  69·2 to 69·3
  67·0
  66·2 to 66·3
  68·3
  66·0 to 64·8
  64·8 to 64·0
  70·5 to 71·3
  68·8 to 68·3
  70·3 to 68·5
  68·3
64·8 to 72·2
70·7 to 49·3
64·2 to 71·2
72·2 to 61·8
65·5 to 69·8
64·0 to 56·0
61·0 to 68·3
64·0 to 75·8
63·7 to 55·7
60·0 to 78·5
65·7 to 55·5
60·0 to 73·8
78·0 to 64·2
70·0 to 55·5
66·0 to 53·0
65·5 to 81·5
75·7 to 58·0
73·0 to 57·0
73·7 to 58·2
69·9
61·7
67·2
64·9
66·0
60·0
64·0
68·5
64·1
69·2
62·8
67·5
71·1
63·0
60·5
71·5
66·1
65·5
65·0
+2·2
+4·5
+2·0
+5·2
+4·2
+6·3
+2·2
–1·2
–0·9
+0·1
+4·2
–1·2
–2·8
+2·4
+3·9
–0·5
+2·5
+3·9
+3·3

* Hole full of rain-water.     † Soil, a moist sand.     § Dry sand.




 

[ 446 ]

 

SERIES V. Jheels, Gangetic Delta, and Chittagong

 

Locality Date Eleva-
tion
(feet)
Depth
(ft. in.)
Temperature
of sunk
Thermometer
Extreme
Temperature
of Air
observed
Approx.
Mean
Temp.
of Air
deduced
Diff.
between
Air and
sunk
Therm.
Silchar
Silhet
Noacolly
Chittagong
Chittagong
Chittagong, flagstaff hill
Hat-hazaree
Sidhee
Hattiah
Seetakoond
Calcutta†
Nov. 27 to 30
Dec. 3 to 7
Dec. 18 to 19
Dec. 23 to 31
Jan. 14 to 16
Dec. 28 to 30
Jan. 4 to 5
Jan. 5 to 6
Jan. 6 to 9
Jan. 9 to 14
Jan. 16 to Feb. 5
116
133
  20
191
 
151
  20
  20
  20
  20
  18
2    7   77·7 to 75·8
  73·5 to 73·7
  73·3
  72·5 to 73·0
  73·3 to 73·7
  72·0 to 71·8
  71·3
  71·0
*67·7
  73·3 to 73·7
  76·0 to 77·0
  55·0 to 81·7
  63·0 to 74·5
  58·5 to 76·5
  53·2 to 75·0
  61·3 to 78·7
  55·2 to 74·2
  50·5 to 62·0
  52·7 to 70·2
  50·2 to 77·5
  55·2 to 79·5
§56·5 to 82·0
69·1
69·5
69·5
63·8
65·5
65·3
65·0
65·0
64·5
70·2
69·3
+7·7
+3·1
+3·8
+9·0
+8·3
+6·6
+6·3
+6·0
+3·2
+3·3
+7·2

* Shaded by trees.     † Observations at the Mint, etc., by Mr. Muller.
§ Observations for temperature of air, taken at the Observatory.

 




 
I.

ON THE DECREMENT OF TEMPERATURE IN ASCENDING THE SIKKIM HIMALAYA MOUNTAINS AND KHASIA MOUNTAINS

 

I have selected as many of my observations for temperature of the sir as appeared to be trustworthy, and which, also, were taken contemporaneously with others at Calcutta, and I have compared them with the Calcutta observations, in order to find the ratio of decrement of heat to an increase of elevation. The results of several sets of observations are grouped together, but show so great an amount of discrepancy, that it is evident that a long series of months and the selection of several stations are necessary in a mountain country to arrive at any accurate results. Even at the stations where the most numerous and the most trustworthy observations were recorded, the results of different months differ extremely; and with regard to the other stations, where few observations were taken, each one is affected differently from another at the same level with it, by the presence or proximity of forest, by exposure to the east or west, to ascending or


 

[ 447 ]

 

descending currents in the valleys, and to cloud or sunshine. Other and still more important modifying influences are to be traced to the monthly variations in the amount of humidity in the air and the strength of its currents, to radiation, and to the evolution of heat which accompanies condensation raising the temperature of elevated regions during the rainy season. The proximity of large masses of snow has not the influence I should have expected in lowering the temperature of the surrounding atmosphere, partly no doubt because of the more rapid condensation of vapours which it effects, and partly because of the free circulation of the currents around it. The difference between the temperatures of adjacent grassy and naked or rocky spots, on the other hand, is very great indeed, the former soon becoming powerfully heated in lofty regions where the sun's rays pass through a rarefied atmosphere, and the rocks especially radiating much of the heat thus accumulated, for long after sunset. In various parts of my journals I have alluded to other disturbing causes, which being all more or leas familiar to meteorologists, I need not recapitulate here. Their combined effects raise all the summer temperatures above what they should theoretically be.

In taking Calcutta as a standard of comparison, I have been guided by two circumstances; first, the necessity of selecting a spot where observations were regularly and accurately made; and secondly, the being able to satisfy myself by a comparison of my instruments that the results should be so far strictly comparable.

I have allowed 1° Fahr. for every degree in latitude intervening between Sikkim and Calcutta, as the probable ratio of diminution of temperature. So far as my observations made in east Bengal and in various parts of the Gangetic delta afford a means of solving this question, this is a near approximation to the truth. The spring observations however which I have made at the foot of the Sikkim Himalaya would indicate a much more rapid decrement; the mean temperature of Titalya and other parts of the plains south of the forests, between March and May being certainly 6°–9° lower than Calcutta: this period however is marked by north-west and north-east winds, and by a strong haze which prevents the sun's rays from impinging on the soil with any effect. During the southerly


 

[ 448 ]

 

winds, the same region is probably hotter than Calcutta, there being but scanty vegetation, and the rain-fall being moderate.

In the following observations solitary readings are always rejected.


 


 

I.—Summer or Rainy Season observations at Dorjiling.

 

Observations taken during the rainy season of 1848, at Mr. Hodgson's (Jillapahar, Dorjiling) alt. 7,430 feet, exposure free to the north east and west, the slopes all round covered with heavy timber; much mist hence hangs over the station. The mean temperatures of the month at Jillapahar are deduced from horary observations, and those of Calcutta from the mean of the daily maximum and minimum.

 

Month No. of
Obs. at
Jillapahar
Temp. Temp.
Calcutta
Equiv.
of
1° Fahr.
July
August
September
October
284
378
407
255
61·7
61·7
58·9
55·3
86·6
85·7
84·7
83·3
364 feet
346 feet
348 feet
316 feet
  1,324    Mean 344 feet


 


 

II.—Winter or dry season observations at Dorjiling.
 

 
1. Observations taken at Mr. J. Muller’s, and chiefly by himself, at “the Dale”;
elev. 6,956 feet; a sheltered spot, with no forest near, and a free west exposure.
103 observations. Months: November, December, January, and February
1°=313 ft.
2. Observations at Dr. Campbell’s (Superintendent’s) house in April;
elev. 6,950 feet; similar exposure to the last.
13 observations in April
1°=308 ft.
3. Observations by Mr. Muller at Colinton; elev. 7,179 feet; free exposure to
north-west; much forest about the station, and a high ridge to east and south.
38 observations in winter months
1°=290 ft.
4. Miscellaneous (11) observations at Leebong; elev. 6000 feet; in February;
free exposure all round
1°=266 ft.
5. Miscellaneous observations at “Smith’s Hotel;” Dorjiling, on a cleared ridge;
exposed all round; elev. 6,863 feet. April and May
1°=252 ft.
————
  Mean of winter observations  
Mean of summer observations

Mean
1°=286 ft.
1°=344 ft.
————
310 ft.



 

[ 449 ]

 


 

III.—Miscellaneous observations taken at different places in Dorjiling, elevations 6,900 to 7,400 feet, with the differences of temperature between Calcutta and Dorjiling.


 
Month Number of
Observations
Difference of
Temperature
Equivalent
January
February
March
April
March and April
July
August
September
October
27
84
37
  7
29
83
74
95
18
30·4
32·8
41·9
36·0
37·3
23·6
22·4
25·7
29·5
1°=287 ft.
1°=265 ft.
1°=196 ft.
1°=236 ft.
1°=224 ft.
1°=389 ft.
1°=415 ft.
1°=350 ft.
1°=297 ft.
  Sum 454 Mean 31·1 Mean 1°=295 ft.

 

These, it will be seen, give a result which approximates to that of the sets I and II. Being deduced from observations at different exposures, the effects of these may be supposed to be eliminated. It is to be observed that the probable results of the addition of November and December's observations, would be balanced by those of May and June, which are hot moist months.


 


 

IV.—Miscellaneous cold weather observations made at various elevations between 1000 and 17,000 feet, during my journey into east Nepal and Sikkim, in November to January 1848 and 1849. The equivalent to 1° Fahr. was deduced from the mean of all the observations at each station, and these being arranged in sets corresponding to their elevations, gave the following results.

 

Elevation Number
of Stations
Number of
Observations
Equivalent
  1,000 to   4,000 ft.
  4,000 to   8,000 ft.
  8,000 to 12,000 ft.
12,000 to 17,000 ft.
27
52
20
14
111
197
  84
  54
1°=215 ft.
1°=315 ft.
1°=327 ft.
1°=377 ft.
  Sum 113 Sum 446 Mean 1°=308 ft.



 

[ 450 ]

 

The total number of comparative observations taken during that journey, amounted to 563, and the mean equivalent was 1°=303 feet, but I rejected many of the observations that were obviously unworthy of confidence.

 


 

V.—Miscellaneous observations (chiefly during the rainy season) taken during my journey into Sikkim and the frontier of Tibet, between May 2nd and December 25th, 1848. The observations were reduced as in the previous instance. The rains on this occasion were unusually protracted, and cannot be said to have ceased till mid-winter, which partly accounts for the very high temperatures.

 

Elevation Number
of Stations
Number of
Observations
Equivalent
  1,000 to   4,000 ft.
  4,000 to   8,000 ft.
  8,000 to 12,000 ft.
12,000 to 17,000 ft.
10
21
18
29
  45
283
343
219
1°=422 ft.
1°=336 ft.
1°=355 ft.
1°=417 ft.
  Sum 78 Sum 890 Mean 1°=383 ft.

 

The great elevation of the temperature in the lowest elevations is accounted for by the heating of the valleys wherein these observations were taken, and especially of the rocks on their floors. The increase with the elevation, of the three succeeding sets, arises from the fact that the loftier regions are far within the mountain region, and are less forest clad and more sunny than the outer Himalaya.

A considerable number of observations were taken during this journey at night, when none are recorded at Calcutta, but which are comparable with contemporaneous observations taken by Mr. Muller at Dorjiling. These being all taken during the three most rainy months, when the temperature varies but very little during the whole twenty-four hours, I expected satisfactory results, but they proved very irregular and anomalous.

The means were—
           At 21 stations of greater elevation than Dorjiling 1°=348 ft.
           At 17 stations lower in elevation 1°=447 ft.

 


 

VI.—Sixty-four contemporaneous observations at Jillapahar, 7,430 feet, and the bed of the Great Rungeet river, 818 feet; taken in January and February, give 1°=322 feet.

 



 

[ 451 ]

 


 

VII.—Observations taken by burying a thermometer two and a half to three feet deep, in a brass tube, at Dorjiling and at various elevations near that station.

 

Month Upper Stations Lower Stations  
February and March
February

April
April
March and April
March, April, May
Jillapahar, 7,430 ft.
    Ditto

Leebong, 6000 ft.
Jillapahar, 7,430 ft.
Khersiong, 4,813 ft.
Jillapahar, 7,430 ft.
Leebong, 6000 ft.
Guard House,
    Great Rungeet, 1,864 ft.
    Ditto
Khersiong, 4,813 ft.
Punkabaree, 1,850 ft.
    Ditto
1°=269 ft.

1°=298 ft.
1°=297 ft.
1°=297 ft.
1°=223 ft.
1°=253 ft.
    Mean 1°=273 ft.


 

The above results would seem to indicate that up to an elevation of 7,500 feet, the temperature diminishes rather more than 1° Fahr. for every 300 feet of ascent or thereabouts; that this decrement is much leas in the summer than in the winter months; and I may add that it is less by day than by night. There is much discrepancy between the results obtained at greater or less elevations than 7000 feet; but a careful study of these, which I have arranged in every possible way, leads me to the conclusion that the proportion map be roughly indicated thus:—


 

1°=300 feet, for elevations from   1,000 to   8,000 feet.
1°=320 feet, for elevations from   8,000 to 10,000 feet.
1°=350 feet, for elevations from 10,000 to 14,000 feet.
1°=400 feet, for elevations from 14,000 to 18,000 feet.

 


 

VIII.—Khasia mountain observations.

 
Date Calcutta
Obs.
Number
of
Obs.
Churra
Obs.
Number
of
Obs.
  Altitude
above
the Sea
Churra Poonji, June 13 to 26
Churra Poonji, Aug. 7 to Sept. 4
Churra Poonji, Oct. 29 to Nov. 16
86·3
84·6
80·7
  63
196
  85
70·1
69·2
63·1
  67
214
133
1°=300 ft.
1°=331 ft.
1°=282 ft.
4,069 ft.
4,225 ft.
4,225 ft.
    354   414 Mean, 304 ft.  




 

[ 452 ]

 

Date Calcutta
Obs.
Number
of
Obs.
Khasia
Obs.
Number
of
Obs.
  Altitude
above
the Sea
Kala-panee, June, Aug., Sept.
Moflong, June, July, Aug., Oct.
Syong
Myrung, Aug.
Myrung, Oct.
Nunklow
Mooshye, Sept. 23
Pomrang, Sept. 23
Amwee, Sept. 23
Joowy, Sept. 23
85·5
85·9
85·1
89·1
82·9
86·4
78·5
82·7
79·9
79·5
35
73
  4
42
21
139  
  9
51
15
11
67·4
68·8
65·0
69·7
63·2
70·9
66·3
65·8
67·1
69·0
35
74
  6
41
58
139  
12
51
11
  7
1°=345 ft.
1°=373 ft.
1°=332 ft.
1°=343 ft.
1°=336 ft.
1°=372 ft.
1°=499 ft.
1°=369 ft.
1°=396 ft.
1°=567 ft.
5,302 ft.
6,062 ft.
5,734 ft.
5,632 ft.
5,632 ft.
4,688 ft.
4,863 ft.
5,143 ft.
4,105 ft.
4,387 ft.
    400   434 1°=385 ft.  


 

The equivalent thus deduced is far greater than that brought out by the Sikkim observations. It indicates a considerably higher temperature of the atmosphere, and is probably attributable to the evolution of heat during extraordinary rain-fall, and to the formation of the surface, which is a very undulating table-land, and everywhere traversed by broad deep valleys, with very steep, often precipitous flanks; these get heated by the powerful sun, and from them, powerful currents ascend. The scanty covering of herbage too over a great amount of the surface, and the consequent radiation of heat from the earth, must have a sensible influence on the mean temperature of the summer months.

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