ELEVATION 16,000 TO 17,000 FEET
| EAST NEPAL ANDSIKKIM | 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 ANDSIKKIM | 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]]