ELEVATION 9000 TO 10,000 FEET

EAST NEPAL AND SIKKIM CALCUTTA
No.
of
Obs.		 Locality Elev. Month Temp. Dew
Point		 Diff. Tens. Temp. Dew
Point		 Diff. Tens.
4
8
4
1
1		 Yangma Guola
Nanki
Singalelah
Sakkiazong
Zemu river		 9279
9320
9295
9322
9828		 Nov.
Nov.
Dec.
Nov.
June		 37·8
42·3
36·2
53·5
60·0		 33·1
38·3
35·7
33·3
47·6		   4·7
  4·0
  0·5
20·2
12·4		 ·207
·249
·227
·209
·343		 72·7
52·2
70·9
80·0
93·3		 61·4
48·3
62·1
57·3
81·9		 11·3
  3·9
  8·8
22·7
11·4		 ·549
·352
·560
·478
1·062  
18       Mean 46·0 37·6   8·4 ·247 73·8 62·2 11·6 ·600
  East Nepal
and Sikkim		 Calcutta
Humidity
Weight of vapour		 0·747
2·80 gr.		 0·724
6·28 gr.

ELEVATION 10,000 TO 11,000 FEET

EAST NEPAL AND SIKKIM CALCUTTA
No.
of
Obs.		 Locality Elev. Month Temp. Dew
Point		 Diff. Tens. Temp. Dew
Point		 Diff. Tens.
13
  5
  4
  2
  2
  4
10
  4
  3
16
17
  9
  8
  9
15
  4		 Tonglo
Nanki
Yalloong river
Tonglo top
Yeunga
Zemu river
Wallanchoon
Laghep
Laghep
Thlonok river, 7 a.m.
Thlonok river, 9.50 a.m.
Thlonok river, noon
Thlonok river, 2.40 p.m.
Thlonok river, 4 p.m.
Thlonok river, sunset
Yangma Valley		 10,008
10,024
10,058
10,079
10,196
10,247
10,384
10,423
10,423
10,486
10,486
10,486
10,486
10,486
10,486
10,999		 May
Nov.
Dec.
May
Oct.
June
Nov.
Nov.
Nov.
June
June
June
June
June
June
Dec.		 51·5
42·8
37·7
49·9
45·9
45·4
37·9
46·0
37·6
48·5
57·6
56·1
54·8
53·4
49·8
31·6		 50·2
35·5
29·6
47·9
44·7
44·2
30·2
42·4
37·0
47·2
51·4
50·6
50·6
50·6
48·9
24·3		 1·3
7·3
8·1
2·0
1·2
1·2
7·7
3·6
0·6
1·3
6·2
5·5
4·2
2·8
0·9
7·3		 ·376
·225
·183
·348
·311
·306
·187
·287
·238
·339
·392
·382
·381
·381
·359
·149		 88·8
79·5
77·7
89·4
79·5
84·6
76·5
80·9
75·3
79·0
87·4
90·0
88·5
88·7
85·5
74·4		 80·8
65·8
62·1
80·5
77·1
75·1
61·9
68·0
69·4
75·1
78·8
79·3
79·7
78·7
78·0
61·9		   8·0
13·7
15·6
  8·9
  2·4
  9·5
14·6
12·9
  5·9
  3·9
  8·6
10·7
  8·8
10·0
  7·5
12·3		 1·030  
·633
·560
1·018  
·915
·856
·558
·681
·712
·856
·965
·979
·991
·962
·938
·558
123       Mean 46·7 42·8 3·8 ·303 82·8 73·3   9·5 ·826
  East Nepal
and Sikkim		 Calcutta
Humidity
Weight of vapour		 0·878
3·35 gr.		 0·740
8·70 gr.

ELEVATION 11,000 TO 12,000 FEET

EAST NEPAL AND SIKKIM CALCUTTA
No.
of
Obs.		 Locality Elev. Month Temp. Dew
Point		 Diff. Tens. Temp. Dew
Point		 Diff. Tens.
  3
  3
  1
12
  6
  8
  5
  6
  6
  2
10
  9
  5
  7
  4
10
  7		 Barfonchen
Punying
Kambachen village
Tallum, 7 a.m.
Tallum, 9.50 a.m.
Tallum, noon
Tallum, 2.40 p.m.
Tallum, 4 p.m.
Tallum, sunset
Kambachen Valley
Yeumtong, 7 a.m.
Yeumtong, 9.50 a.m.
Yeumtong, noon
Yeumtong 2.40 p.m.
Yeumtong, 4 p.m.
Yeumtong, sunset
Yeumtong, Miscellaneous		 11,233
11,299
11,378
11,482
11,482
11,482
11,482
11,482
11,482
11,484
11,887
11,887
11,887
11,887
11,887
11,887
11,887		 Nov.
Aug.
Dec.
July
July
July
July
July
July
Dec.
| 
| Aug.,
| Sep.,
| and
| Oct.
| 
Oct.		 36·8
50·2
43·3
50·4
58·1
57·9
55·7
54·3
48·8
30·4
44·4
53·6
54·5
48·8
48·4
42·0
43·5		 31·9
49·5
32·5
47·8
50·5
50·8
50·2
50·1
47·3
26·0
43·8
48·9
48·3
47·4
47·1
35·9
37·1		 4·9
0·7
10·8  
2·6
7·6
7·1
5·5
4·2
1·5
4·4
0·6
4·7
6·2
1·4
1·3
6·1
6·4		 ·198
·367
·203
·347
·380
·384
·377
·375
·340
·161
·302
·360
·353
·342
·338
·229
·239		 76·3
84·5
80·0
85·0
88·1
89·7
89·3
90·3
86·6
69·9
83·0
87·5
89·7
87·2
85·2
60·6
83·7		 69·6
78·8
61·2
80·3
79·7
81·3
80·6
79·4
80·0
59·5
78·9
78·7
77·2
77·2
77·8
58·5
69·7		   6·7
  5·7
18·8
  4·7
  8·4
  8·4
  8·7
10·9
  6·6
10·4
  4·1
  8·8
12·5
10·0
  7·4
  2·1
14·0		   ·719
  ·963
  ·544
1·010
  ·993
1·043
1·020
  ·981
1·001
  ·515
  ·967
  ·959
  ·917
  ·915
  ·934
  ·497
  ·720
104       Mean 48·3 43·8   4·5 ·311 83·3 74·6   8·7   ·865
  East Nepal
and Sikkim		 Calcutta
Humidity
Weight of vapour		 0·860
3·46 gr.		 0·760
9·00 gr.

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.

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.

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 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.[433]

[433] 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.

The great amount of relative humidity registered at 6000 to 8000 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 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.”