Chapter XXXI: Appendix: G

ON THE RELATIVE HUMIDITY, AND ABSOLUTE AMOUNT OF VAPOUR CONTAINED IN THE ATMOSPHERE AT DIFFERENT ELEVATIONS IN THE SIKKIM HIMALAYA.

My observations for temperature and wet-bulb being for the most part desultory, taken at different dates, and under very different conditions of exposure, etc., it is obvious that those at one station are hardly, if at all, comparative with those of another, and I have therefore selected only such as were taken at the same date and hour with others taken at the Calcutta Observatory, or as can easily be reduced; which thus afford a standard (however defective in many respects) for a comparison. I need hardly remind my reader that the vapour-charged wind of Sikkim is the southerly one, which blows over Calcutta; that in its passage northwards to Sikkim in the summer months, it traverses the heated plains at the foot of the Himalaya, and ascending that range, it discharges the greater part of its moisture (120 to 140 inches annually) over the outer Himalayan ranges, at elevations of 4000 to 8000 feet. The cooling effect of the uniform covering of forest on the Sikkim ranges is particularly favourable to this deposition, but the slope of the mountains being gradual, the ascending currents are not arrested and cooled so suddenly as in the Khasia mountains, where the discharge is consequently much greater. The heating of the atmosphere, too, over the dry plains at the foot of the outer range, increases farther its capacity for the retention of vapour, and also tends to render the rain-fall less sudden and violent than on the Khasia, where the south wind blows over the cool expanse of the Jheels. It will be seen from the following observations, that in Sikkim the relative humidity of the atmosphere remains pretty constantly very high in the summer months, and at all elevations, except in the rearward valleys; and even there a humid atmosphere prevails up to 14,000 feet, everywhere within the influence of the snowy mountains. The uniformly high temperature which prevails throughout the summer, even at elevations of 17,000 and 18,000 feet, is no doubt proximately due to the evolution of heat during the condensation of these vapours. It will be seen by the pages of my journal, that continued sunshine, and the consequent heating of the soil, is almost unknown during the summer, at any elevation on the outer or southward ranges of Dorjiling: but the sunk thermometer proves that in advancing northward into the heart of the mountains and ascending, the sun's effect is increased, the temperature of the earth becoming in summer considerably higher than that of the air. With regard to the observations themselves, they may be depended upon as comparable with those of Calcutta, the instruments having been carefully compared, and the cases of interpolation being few. The number of observations taken at each station is recorded in a separate column; where only one is thus recorded, it is not to be regarded as a single reading, but the mean, of several taken during an hour or longer period. I have rejected all solitary observations, even when accompanied by others at Calcutta; and sundry that were, for obvious reasons, likely to mislead. Where many observations were taken at one place, I have divided them into sets, corresponding to the hours at which alone the Calcutta temperature and wet-bulb thermometer are recorded,* [Sunrise; 9.50 a.m.; noon; 2.40 p.m.; 4 p.m., and sunset.] in order that meteorologists may apply them to the solution of other questions relating to the distribution of heat and moisture. The Dorjiling observations, and those in the immediate neighbourhood of that station, appeared to me sufficiently numerous to render it worth while classing them in months, and keeping them in a series by themselves. The tensions of vapour are worked from the wet-bulb readings by Apjohn's formula and tables, corrected for the height of the barometer at the time. The observations, except where otherwise noted, are taken by myself.

SERIES I. _Observations made at or near Dorjiling._

JANUARY, 1849

DORJILING No. of Obs. Place Elev. Hour Tp. D.P. Diff. Tens. --------------------------------------------------------------------- 15 The Dale* 6956 ft. 9.50 a.m. 42.9 32.4 10.5 .202 15 Mr. Muller's ... Noon 45.8 33.8 12.0 .212 10 ... ... 2.40 p.m. 48.3 37.4 10.9 .241 8 ... ... 4 p.m. 48.6 37.8 10.8 .244 9 ... ... Sunset 46.5 37.1 9.4 .238 --------------------------------------------------------------------- 57 ... ... Mean 46.4 35.7 10.7 .227 ---------------------------------------------------------------------

CALCUTTA No. of Obs. Place Elev. Hour Tp. D.P. Diff. Tens. --------------------------------------------------------------------- 15 The Dale* 6956 ft. 9.50 a.m. 67.5 55.3 12.2 .446 15 Mr. Muller's ... Noon 72.9 55.7 17.2 .455 10 ... ... 2.40 p.m. 76.1 55.1 21.0 .444 8 ... ... 4 p.m. 75.1 54.8 20.3 .440 9 ... ... Sunset 71.8 54.9 16.9 .441 --------------------------------------------------------------------- 57 ... ... Mean 72.7 55.2 17.5 .445 ---------------------------------------------------------------------

*Observations to which the asterisk is affixed were taken by Mr. Muller.

Dorjiling.--Humidity 0.700 Calcutta 0.562
,, Vapour in cubic foot
of atmosphere 2.63 gr. ,, 4.86 gr.

JANUARY, 1850 DORJILING No. of Obs. Place Elev. Hour Tp. D.P. Diff. Tens. --------------------------------------------------------------------- 3 Jillapahar, 7430 ft. Sunrise 32.8 30.1 2.7 .186 6 Mr. Hodgson's ... 9.50 a.m. 39.5 34.7 4.8 .219 3 ... ... Noon 42.4 38.0 4.4 .246 5 ... ... 2.40 p.m. 41.9 37.8 4.1 .244 5 ... ... 4 p.m. 41.1 38.5 2.6 .250 5 ... ... Sunset 38.7 35.6 3.1 .226 13 ... ... Miscel. 41.9 39.9 2.0 .263 4 Saddle of road 7412 ft. Do. 41.1 36.4 4.7 .233 at Sinchul. 1 Pacheem. 7258 ft. Do. 39.8 38.7 1.1 .252 --------------------------------------------------------------------- 45 ... ... Mean 39.9 36.6 3.3 .235 ---------------------------------------------------------------------

CALCUTTA No. of Obs. Place Elev. Hour Tp. D.P. Diff. Tens. --------------------------------------------------------------------- 3 Jillapahar, 7430 ft. Sunrise 51.5 48.5 3.0 .354 6 Mr. Hodgson's ... 9.50 a.m. 66.9 55.1 11.8 .444 3 ... ... Noon 74.1 51.7 22.4 .395 5 ... ... 2.40 p.m. 78.3 51.4 26.9 .391 5 ... ... 4 p.m. 77.4 59.5 17.9 .514 5 ... ... Sunset 72.4 54.7 17.7 .438 13 ... ... Miscel. 77.9 60.1 17.8 .525 4 Saddle of road 7412 ft. Do. 67.7 57.2 10.5 .476 at Sinchul. 1 Pacheem. 7258 ft. Do. 71.6 50.5 21.2 .379 --------------------------------------------------------------------- 45 ... ... Mean 70.9 54.3 16.6 .435 ---------------------------------------------------------------------

Dorjiling.--Humidity 0.890 Calcutta 0.580
,, Weight of vapour 2.75 gr. ,, 4.86 gr.

FEBRUARY DORJILING No. of Obs. Place Elev. Hour Tp. D.P. Diff. Tens. --------------------------------------------------------------------- 3 Jillapahar, 7430 ft. Sunrise 36.9 34.7 2.2 .219 18 1850 ... 9.50 a.m. 42.9 38.6 4.3 .251 12 ... ... Noon 44.8 41.3 3.5 .276 12 ... ... 2.40 p.m. 44.8 37.4 7.4 .241 17 ... ... 4 p.m. 44.0 35.6 8.4 .226 19 ... ... Sunset 42.4 35.8 6.6 .228 13 The Dale* 6956 ft. Miscel. 40.8 35.1 5.7 .222 --------------------------------------------------------------------- 97 ... ... Mean 42.4 36.9 5.4 .238 ---------------------------------------------------------------------

CALCUTTA No. of Obs. Place Elev. Hour Tp. D.P. Diff. Tens. --------------------------------------------------------------------- 3 Jillapahar, 7430 ft. Sunrise 60.0 54.2 5.8 .431 18 1850 ... 9.50 a.m. 72.8 58.8 14.0 .503 12 ... ... Noon 79.8 58.7 21.2 .501 12 ... ... 2.40 p.m. 82.4 57.9 24.5 .487 17 ... ... 4 p.m. 81.1 58.1 23.0 .492 19 ... ... Sunset 76.3 60.7 15.6 .536 13 The Dale* 6956 ft. Miscel. 69.9 59.8 10.1 .518 --------------------------------------------------------------------- 97 ... ... Mean 74.6 58.3 16.3 .495 ---------------------------------------------------------------------

Dorjiling.--Humidity 0.828 Calcutta 0.590
,, Weight of vapour 2.75 gr. ,, 5.40 gr.

MARCH DORJILING No. of Obs. Place Elev. Hour Tp. D.P. Diff. Tens. --------------------------------------------------------------------- 10 Jillapahar, 7430 ft. 9.50 a.m. 44.2 42.7 1.5 .290 8 1850 ... Noon 45.5 43.0 2.5 .293 5 ... ... 2.40 p.m. 46.4 44.0 2.4 .303 8 ... ... 4 p.m. 45.5 43.4 2.1 .297 6 ... ... Sunset 43.1 41.5 1.6 .278 3 Pacheem. 7258 ft. Misc. 44.8 44.6 0.2 .310 --------------------------------------------------------------------- 40 ... ... Mean 44.9 43.2 1.7 .295 ---------------------------------------------------------------------

CALCUTTA No. of Obs. Place Elev. Hour Tp. D.P. Diff. Tens. --------------------------------------------------------------------- 10 Jillapahar, 7430 ft. 9.50 a.m. 81.6 64.1 17.5 .602 8 1850 ... Noon 88.2 57.0 31.2 .472 5 ... ... 2.40 p.m. 91.3 53.2 38.1 .416 8 ... ... 4 p.m. 90.1 52.0 38.1 .399 6 ... ... Sunset 82.9 63.7 19.2 .590 3 Pacheem. 7258 ft. Misc. 85.0 74.8 10.2 .848 --------------------------------------------------------------------- 40 ... ... Mean 86.5 60.8 25.7 .555 ---------------------------------------------------------------------

Dorjiling.--Humidity 0.940 Calcutta 0.438
,, Weight of vapour 3.42 gr. ,, 5.72 gr.

APRIL DORJILING No. of Obs. Place Elev. Hour Tp. D.P. Diff. Tens. --------------------------------------------------------------------- 3 Jillapahar, 7430 ft. 9.50 a.m. 57.0 40.2 16.8 .266 3 1849 ... Noon 59.8 44.1 15.7 .305 1 ... ... 2.40 p.m. 60.2 44.4 15.8 .308 7 Dr. Campbell's 6932 ft. 9.50 a.m. 61.8 53.3 8.5 .417 2 1850 ... Noon 65.4 52.8 12.6 .411 4 ... ... 4 p.m. 57.5 53.7 13.8 .423 3 ... ... Sunset 56.9 51.4 5.5 .392 --------------------------------------------------------------------- 23 ... ... Mean 59.8 48.6 11.3 .360 ---------------------------------------------------------------------

CALCUTTA No. of Obs. Place Elev. Hour Tp. D.P. Diff. Tens. --------------------------------------------------------------------- 3 Jillapahar, 7430 ft. 9.50 a.m. 90.3 71.3 19.0 .758 3 1849 ... Noon 97.0 64.5 32.5 .607 1 ... ... 2.40 p.m. 97.7 73.4 24.3 .812 7 Dr. Campbell's 6932 ft. 9.50 a.m. 86.7 66.3 20.4 .644 2 1850 ... Noon 91.3 68.8 22.5 .699 4 ... ... 4 p.m. 88.6 72.1 16.5 .778 3 ... ... Sunset 82.8 73.0 9.8 .800 --------------------------------------------------------------------- 23 ... ... Mean 90.6 69.9 20.7 .728 ---------------------------------------------------------------------

Dorjiling.--Humidity 0.684 Calcutta 0.523
,, Weight of vapour 3.98 gr. ,, 7.65 gr.

MAY DORJILING No. of Obs. Place Elev. Hour Tp. D.P. Diff. Tens. --------------------------------------------------------------------- 3 Smith's Hotel, 6863 ft. Misc. 57.2 55.0 2.2 .443 1848 45 Colinton,* 7179 ft. Misc. 60.4 57.9 12.5 .466 1849 --------------------------------------------------------------------- 48 ... ... Mean 58.8 56.5 12.4 .455 ---------------------------------------------------------------------

CALCUTTA No. of Obs. Place Elev. Hour Tp. D.P. Diff. Tens. --------------------------------------------------------------------- 3 Smith's Hotel, 6863 ft. Misc. 88.6 78.4 10.2 .951 1848 45 Colinton,* 7179 ft. Misc. 90.0 77.2 12.8 .917 1849 --------------------------------------------------------------------- 48 ... ... Mean 89.3 77.8 11.5 .934 ---------------------------------------------------------------------

Dorjiling.--Humidity 0.926 Calcutta 0.698
,, Weight of vapour 5.22 gr. ,, 9.90 gr.

JUNE DORJILING No. of Obs. Place Elev. Hour Tp. D.P. Diff. Tens. --------------------------------------------------------------------- 40 Colinton* 7179 ft. Misc. 60.9 57.6 13.3 .483 ---------------------------------------------------------------------

CALCUTTA No. of Obs. Place Elev. Hour Tp. D.P. Diff. Tens. --------------------------------------------------------------------- 40 Colinton* 7179 ft. Misc. 85.5 78.4 7.1 .952 ---------------------------------------------------------------------

Dorjiling.--Humidity 0.895 Calcutta 0.800
,, Weight of vapour 5.39 gr. ,, 10.17 gr.

JULY DORJILING No. of Obs. Place Elev. Hour Tp. D.P. Diff. Tens. --------------------------------------------------------------------- 18 Jillapahar, 7430 ft. 9.50 a.m. 63.2 61.4 1.8 .548 25 1848 ... Noon 65.0 62.6 2.4 .570 24 ... ... 2.40 p.m. 64.7 62.3 2.4 .565 16 ... ... 4 p.m. 63.8 61.5 2.3 .550 31 The Dale,* 6952 ft. 6 a.m. 60.2 58.7 1.5 .537 31 1848 ... 2 p.m. 66.3 63.3 3.0 .621 31 ... ... 6 p.m. 63.0 60.9 2.1 .575 --------------------------------------------------------------------- 176 ... ... Mean 63.7 61.5 2.2 .567 ---------------------------------------------------------------------

CALCUTTA No. of Obs. Place Elev. Hour Tp. D.P. Diff. Tens. --------------------------------------------------------------------- 18 Jillapahar, 7430 ft. 9.50 a.m. 87.0 79.4 7.6 .983 25 1848 ... Noon 89.0 80.0 9.0 1.001 24 ... ... 2.40 p.m. 88.1 79.4 8.7 .983 16 ... ... 4 p.m. 87.2 79.5 7.7 .985 31 The Dale,* 6952 ft. 6 a.m. 81.3 79.0 2.3 .969 31 1848 ... 2 p.m. 88.0 79.6 8.4 .989 31 ... ... 6 p.m. 84.8 79.2 5.6 .977 --------------------------------------------------------------------- 176 ... ... Mean 86.5 79.4 7.0 .984 ---------------------------------------------------------------------

Dorjiling.--Humidity 0.929 Calcutta 0.800
,, Weight of vapour 6.06 gr. ,, 10.45 gr.

AUGUST DORJILING No. of Obs. Place Elev. Hour Tp. D.P. Diff. Tens. --------------------------------------------------------------------- 23 Jillapahar, 7430 ft. 9.50 a.m. 64.2 62.4 1.8 .567 21 1848 ... Noon 64.7 63.3 1.4 .584 17 ... ... 2.40 p.m. 64.7 62.8 1.9 .574 13 ... ... 4 p.m. 63.9 62.5 1.4 .568 31 The Dale,* 6952 ft. 6 a.m. 60.5 59.5 1.0 .551 31 1848 ... 2 p.m. 65.3 63.6 1.7 .628 31 ... ... 6 p.m. 62.8 61.8 1.0 .591 --------------------------------------------------------------------- 167 ... ... Mean 63.7 62.3 1.5 .580 ---------------------------------------------------------------------

CALCUTTA No. of Obs. Place Elev. Hour Tp. D.P. Diff. Tens. --------------------------------------------------------------------- 23 Jillapahar, 7430 ft. 9.50 a.m. 85.8 79.1 6.7 .973 21 1848 ... Noon 87.2 79.2 8.0 .976 17 ... ... 2.40 p.m. 87.4 79.3 8.1 .979 13 ... ... 4 p.m. 86.5 79.5 7.0 .984 31 The Dale,* 6952 ft. 6 a.m. 80.8 78.8 2.0 .962 31 1848 ... 2 p.m. 87.2 79.2 8.0 .976 31 ... ... 6 p.m. 83.7 78.7 5.0 .959 --------------------------------------------------------------------- 167 ... ... Mean 85.5 79.1 6.4 .973 ---------------------------------------------------------------------

Dorjiling.--Humidity 0.955 Calcutta 0.818
,, Weight of vapour 6.25 gr. ,, 10.35 gr.

SEPTEMBER DORJILING No. of Obs. Place Elev. Hour Tp. D.P. Diff. Tens. --------------------------------------------------------------------- 28 Jillapahar, 7430 ft. 9.50 a.m. 60.8 59.3 1.5 .511 23 1848 ... Noon 62.4 60.3 2.1 .528 23 ... ... 2.40 p.m. 62.4 59.6 2.8 .516 21 ... ... 4 p.m. 62.0 59.6 2.4 .516 30 The Dale,* 6952 ft. 6 a.m. 57.4 56.2 1.2 .495 30 1848 ... 2 p.m. 64.9 60.8 4.1 .573 30 ... ... 6 p.m. 60.8 59.0 1.8 .543 --------------------------------------------------------------------- 185 ... ... Mean 61.5 59.3 2.3 .526 ---------------------------------------------------------------------

CALCUTTA No. of Obs. Place Elev. Hour Tp. D.P. Diff. Tens. --------------------------------------------------------------------- 28 Jillapahar, 7430 ft. 9.50 a.m. 87.0 78.4 8.6 .952 23 1848 ... Noon 88.5 78.1 10.4 .943 23 ... ... 2.40 p.m. 88.1 77.4 10.7 .922 21 ... ... 4 p.m. 86.9 77.1 9.8 .914 30 The Dale,* 6952 ft. 6 a.m. 80.9 78.3 2.6 .948 30 1848 ... 2 p.m. 88.8 77.4 11.4 .923 30 ... ... 6 p.m. 84.7 76.6 8.1 .899 --------------------------------------------------------------------- 185 ... ... Mean 86.4 77.6 8.8 .929 ---------------------------------------------------------------------

Dorjiling.--Humidity 0.932 Calcutta 0.760
,, Weight of vapour 5.72 gr. ,, 9.88 gr.

OCTOBER DORJILING No. of Obs. Place Elev. Hour Tp. D.P. Diff. Tens. --------------------------------------------------------------------- 6 Jillapahar, 7430 ft. Noon 55.9 55.3 0.6 .446 6 1848 ... 2.40 p.m. 55.7 54.9 0.8 .440 6 ... ... 4 p.m. 55.6 54.9 0.7 .441 4 Goong. 7436 ft. Misc. 48.3 48.3 0.0 .352 8 ditto 7441 ft. ditto 51.2 50.2 1.0 .376 8 The Dale* 6952 ft. 6 a.m. 55.2 52.7 2.5 .439 17 ... ... 2 p.m. 61.4 56.3 5.1 .497 19 ... ... 6 p.m. 56.9 54.2 2.7 .463 --------------------------------------------------------------------- 74 ... ... Mean 55.0 53.4 1.7 .432 ---------------------------------------------------------------------

CALCUTTA No. of Obs. Place Elev. Hour Tp. D.P. Diff. Tens. --------------------------------------------------------------------- 6 Jillapahar, 7430 ft. Noon 84.4 75.3 9.1 .863 6 1848 ... 2.40 p.m. 86.0 73.3 12.7 .808 6 ... ... 4 p.m. 85.2 74.4 10.8 .837 4 Goong. 7436 ft. Misc. 81.2 73.7 7.5 .819 8 ditto 7441 ft. ditto 80.7 66.9 13.8 .657 8 The Dale* 6952 ft. 6 a.m. 76.1 74.2 1.9 .834 17 ... ... 2 p.m. 87.0 71.2 15.8 .756 19 ... ... 6 p.m. 82.8 73.9 8.9 .824 --------------------------------------------------------------------- 74 ... ... Mean 82.9 72.9 10.1 .800 ---------------------------------------------------------------------

Dorjiling.--Humidity 0.950 Calcutta 0.658
,, Weight of vapour 4.74 gr. ,, 8.55 gr.

NOVEMBER AND DECEMBER DORJILING No. of Obs. Place Elev. Hour Tp. D.P. Diff. Tens. --------------------------------------------------------------------- 4 The Dale,* 6952 ft. 6 a.m. 45.6 41.4 4.2 .277 8 Nov. & Dec. ... 2 p.m. 60.0 48.3 11.7 .355 6 1848 ... 6 p.m. 50.6 44.7 5.9 .311 9 December, ... 2 p.m. 49.7 41.7 8.0 .280 19 1848 ... 6 p.m. 44.0 40.5 3.5 .269 --------------------------------------------------------------------- 46 ... ... Mean 49.9 43.3 6.7 .298 ---------------------------------------------------------------------

CALCUTTA No. of Obs. Place Elev. Hour Tp. D.P. Diff. Tens. --------------------------------------------------------------------- 4 The Dale,* 6952 ft. 6 a.m. 67.9 64.7 3.2 .610 8 Nov. & Dec. ... 2 p.m. 83.3 65.2 18.1 .621 6 1848 ... 6 p.m. 77.3 63.1 14.2 .579 9 December, ... 2 p.m. 79.3 59.0 20.3 .505 19 1848 ... 6 p.m. 75.8 62.6 13.2 .569 --------------------------------------------------------------------- 46 ... ... Mean 76.7 62.9 13.8 .577 ---------------------------------------------------------------------

Dorjiling.--Humidity 0.798 Calcutta 0.640
,, Weight of vapour 3.40 gr. ,, 6.27 gr.

_Comparison of Dorjiling and Calutta._

HUMIDITY

No. of Diff. Obs. Month Dorjiling Calcutta Dorjiling --------------------------------------------------------- 102 January -.795 .571 +.224 97 February .828 .590 +.238 40 March .940 -.438 +.502 23 April .684 .523 +.161 48 May .926 .698 +.228 40 June .895 .800 +.095 176 July .929 .800 +.129 167 August +.955 +.818 +.136 185 September .932 .760 +.172 74 October .950 .658 +.292 46 Nov. and Dec. .798 .640 +.158 ---------------------------------------------------------- 998 Mean 0.876 0.663 +.212

WEIGHT OF VAPOUR IN CUBIC FOOT OF AIR

No. of Diff. Obs. Month Dorjiling Calcutta Calcutta -------------------------------------------------------- 102 January -2.68 -4.80 +2.12 97 February 2.75 5.40 +2.65 40 March 3.42 5.72 +2.30 23 April 3.98 7.65 +3.67 48 May 5.22 9.90 +4.62 40 June 5.39 10.17 +4.78 176 July 6.06 10.05 +3.99 167 August +6.25 +10.35 +4.10 185 September 5.72 9.88 +4.16 74 October 4.74 8.55 +3.81 46 Nov. and Dec. 3.40 6.27 +2.87 -------------------------------------------------------- 998 Mean 4.51 8.07 +3.55

It is hence evident, from nearly 1,000 comparative observations, that the atmosphere is relatively more humid at Dorjiling than at Calcutta, throughout the year. As the southerly current, to which alone is due all the moisture of Sikkim, traverses 200 miles of land, and discharges from sixty to eighty inches of rain before arriving at Dorjiling, it follows that the whole atmospheric column is relatively drier over the Himalaya than over Calcutta; that the absolute amount of vapour, in short, is less than it would otherwise be at the elevation of Dorjiling, though the relative humidity is so great. A glance at the table at the end of this section appears to confirm this; for it is there shown that, at the base of the Himalaya, at an elevation of only 250 feet higher than Calcutta, the absolute amount of vapour is less, and of relative humidity greater, than at Calcutta.

SERIES II.--_Observations at various Stations and Elevations in the Himalaya of East Nepal and Sikkim._

ELEVATION 735 TO 2000 FEET. EASTERN NEPAL AND SIKKIM. No. of Obs. Locality Elev. Month Tem. D.P. Diff. Tens --------------------------------------------------------------------- 3 Katong Ghat. 735 Dec. 60.2 55.3 4.9 .447 Teesta river 2 Great Rungeet, at bridge 818 April 82.8 63.5 19.3 .588 1 Ditto 818 May 77.8 60.3 17.5 .528 3 Tambur river, E. Nepal 1388 Nov. 60.6 57.0 3.6 .473 1 Ditto 1457 Nov. 64.2 59.1 5.1 .507 6 Bhomsong, Teesta river 1596 Dec. 58.6 52.0 6.6 .399 1 Ditto 1596 May 68.2 66.4 1.8 .647 5 Little Rungeet 1672 Jan. 51.0 50.2 0.8 .377 5 Pemiongchi, Great Rungeet 1840 Dec. 54.6 53.7 0.9 .424 11 Punkabaree 1850 March 70.1 55.6 14.5 .472 Ditto 1850 May 73.5 68.3 5.2 .687 10 Guard house 1864 April 73.7 63.8 9.9 .592 (Gt. Rungeet) --------------------------------------------------------------------- 48 Mean 66.3 58.8 7.5 .512

CALCUTTA. No. of Obs. Locality Elev. Month Tem. D.P. Diff. Tens --------------------------------------------------------------------- 3 Katong Ghat. 735 Dec. 73.2 56.7 16.5 .468 Teesta river 2 Great Rungeet, at bridge 818 April 95.8 61.9 33.9 .557 1 Ditto 818 May 91.7 78.3 13.4 .947 3 Tambur river, E. Nepal 1388 Nov. 73.3 62.7 10.6 .571 1 Ditto 1457 Nov. 77.3 63.4 13.9 .585 6 Bhomsong, Teesta river 1596 Dec. 71.6 57.0 14.6 .474 1 Ditto 1596 May 82.6 77.4 5.2 .923 5 Little Rungeet 1672 Jan. 58.5 58.0 0.5 .489 5 Pemiongchi, Great Rungeet 1840 Dec. 73.5 66.2 7.3 .642 11 Punkabaree 1850 March 79.2 62.6 16.6 .570 Ditto 1850 May 83.7 77.9 5.8 .938 10 Guard house 1864 April 92.4 67.0 25.4 .660 (Gt. Rungeet) --------------------------------------------------------------------- 48 Mean 79.4 65.8 13.6 .652

Humidity 0.717 Calcutta 0.663 Weight of vapour 5.57 gr. ,, 6.88 gr.

ELEVATION 2000 TO 3000 FEET. EASTERN NEPAL AND SIKKIM. No. of Obs. Locality Elev. Month Tem. D.P. Diff. Tens --------------------------------------------------------------------- 2 Singdong 2116 Dec. 60.5 53.4 7.1 .419 8 Mywa Guola, E. Nepal 2132 Nov. 66.2 57.5 8.7 .481 3 Pemmi river, E. Nepal 2256 Nov. 55.6 53.9 1.7 .426 3 Tambur river, E. Nepal 2545 Nov. 57.3 51.6 5.7 .394 2 Blingbong (Teesta) 2684 May 72.6 64.0 8.6 .597 8 Lingo (Teesta) 2782 May 75.8 67.3 8.5 .666 12 Serriomsa (Teesta) 2820 Dec. 64.1 56.8 7.3 .469 8 Lingmo (Teesta) 2849 May 68.6 64.6 4.0 .610 3 Ditto 2952 Dec. 56.4 53.5 2.9 .420 --------------------------------------------------------------------- 49 Mean 64.1 58.1 6.1 .498

ELEVATION 2000 TO 3000 FEET. EASTERN NEPAL AND SIKKIM. No. of Obs. Locality Elev. Month Tem. D.P. Diff. Tens --------------------------------------------------------------------- 2 Singdong 2116 Dec. 72.1 52.9 19.2 .411 8 Mywa Guola, E. Nepal 2132 Nov. 75.7 68.7 7.0 .697 3 Pemmi river, E. Nepal 2256 Nov. 62.9 62.3 0.6 .566 3 Tambur river, E. Nepal 2545 Nov. 75.0 63.7 11.3 .591 2 Blingbong (Teesta) 2684 May 81.7 73.6 8.1 .817 8 Lingo (Teesta) 2782 May 90.7 77.7 13.0 .932 12 Serriomsa (Teesta) 2820 Dec. 70.8 62.4 8.4 .567 8 Lingmo (Teesta) 2849 May 87.9 74.9 13.0 .851 3 Ditto 2952 Dec. 69.5 66.5 3.0 .647 --------------------------------------------------------------------- 49 Mean 76.3 67.0 9.3 .675

Humidity 0.820 Calcutta 0.740 Weight of vapour 5.45 gr. ,, 7.13 gr.

ELEVATION 3000 TO 4000 FEET. EASTERN NEPAL AND SIKKIM. No. of Obs. Locality Elev. Month Tem. D.P. Diff. Tens --------------------------------------------------------------------- 5 Kulhait river 3159 Jan. 49.8 47.0 2.8 .337 9 Ratong river 3171 Jan. 44.2 43.0 1.2 .294 3 Tambur river 3201 Nov. 53.0 50.0 3.0 .373 2 Chingtam 3404 Nov. 54.8 49.0 5.8 .360 2 Tikbotang 3763 Dec. 56.5 53.4 3.1 .419 7 Myong Valley 3782 Oct. 61.4 58.4 3.0 .496 7 Iwa river 3783 Dec. 47.5 45.6 1.9 .321 1 Ratong river 3790 Jan. 56.2 41.1 15.1 .275 3 Tukcham 3849 Nov. 68.8 65.4 3.4 .625 1 Pacheem village 3855 Jan. 54.5 46.3 8.2 .329 1 Yankoon 3867 Dec. 50.0 43.6 6.4 .299 2 Mikk 3912 May 66.1 63.9 2.2 .595 5 Sunnook 3986 Dec. 47.9 45.5 2.4 .320 --------------------------------------------------------------------- 48 Mean 54.7 50.2 4.5 .388

CALCUTTA. No. of Obs. Locality Elev. Month Tem. D.P. Diff. Tens --------------------------------------------------------------------- 5 Kulhait river 3159 Jan. 65.8 57.3 8.5 .477 9 Ratong river 3171 Jan. 69.9 56.6 13.3 .466 3 Tambur river 3201 Nov. 72.9 63.2 9.7 .582 2 Chingtam 3404 Nov. 74.9 73.0 1.9 .302 2 Tikbotang 3763 Dec. 68.0 61.8 6.2 .555 7 Myong Valley 3782 Oct. 80.7 71.2 9.5 .755 7 Iwa river 3783 Dec. 73.3 64.7 8.6 .611 1 Ratong river 3790 Jan. 75.8 53.0 22.8 .414 3 Tukcham 3849 Nov. 83.7 76.8 6.9 .904 1 Pacheem village 3855 Jan. 73.6 59.4 14.2 .513 1 Yankoon 3867 Dec. 69.1 63.8 5.3 .593 2 Mikk 3912 May 84.3 75.1 9.2 .856 5 Sunnook 3986 Dec. 69.4 61.1 8.3 .542 --------------------------------------------------------------------- 48 Mean 74.0 64.4 9.6 .621

Humidity 0.858 Calcutta 0.732 Weight of vapour 4.23 gr. ,, 6.60 gr.

ELEVATION 4000 TO 5000 FEET. EASTERN NEPAL AND SIKKIM. No. of Obs. Locality Elev. Month Tem. D.P. Diff. Tens --------------------------------------------------------------------- 3 Yangyading 4111 Dec. 52.0 43.6 8.4 .300 4 Gorh 4128 May. 66.4 59.0 7.4 .506 2 Namgah 4229 Oct. 57.2 54.1 3.1 .429 3 Taptiatok (Tambur) 4283 Nov. 51.3 45.8 5.5 .323 7 Myong Valley 4345 Oct. 59.1 57.8 1.3 .487 3 Jummanoo 4362 Nov. 60.4 50.0 10.4 .374 6 Nampok 4377 Dec. 49.6 49.1 0.5 .362 7 Chakoong 4407 May 57.8 57.6 0.2 .483 10 Singtam 4426 May 62.4 61.7 0.7 .553 5 Namten 4483 Dec. 44.7 44.3 0.4 .307 5 Purmiokshong 4521 Nov. 60.5 56.5 4.0 .466 2 Rungniok 4565 Jan. 54.7 44.3 10.4 .307 16 Singtam 4575 O.&N. 63.8 60.1 3.7 .525 6 Cheadam 4653 Dec. 51.4 46.6 4.8 .332 4 Sablakoo 4676 Dec. 50.0 44.9 5.2 .314 4 Bheti 4683 Nov. 59.0 52.3 6.7 .405 2 Temi 4771 May 59.8 50.1 9.7 .374 4 Lingtam 4805 May 60.4 56.6 3.8 .467 7 Khersiong 4813 Jan. 51.0 45.2 5.8 .316 6 Ditto 4813 March 53.6 45.5 8.1 .320 3 Tassiding 4840 Dec. 52.0 46.6 5.4 .333 6 Lingcham 4870 Dec. 48.5 46.1 2.4 .327 11 Dikkeeling 4952 Dec. 62.0 55.3 6.7 .447 9 Tehonpong 4978 Jan. 49.4 34.7 14.7 .219 --------------------------------------------------------------------- 137 Mean 55.7 50.4 5.4 .387

CALCUTTA. No. of Obs. Locality Elev. Month Tem. D.P. Diff. Tens --------------------------------------------------------------------- 3 Yangyading 4111 Dec. 71.1 67.2 3.9 .663 4 Gorh 4128 May. 85.5 74.2 11.3 .834 2 Namgah 4229 Oct. 80.8 73.7 7.1 .819 3 Taptiatok (Tambur) 4283 Nov. 73.3 64.8 8.5 .614 7 Myong Valley 4345 Oct. 81.7 72.9 8.8 .797 3 Jummanoo 4362 Nov. 77.4 70.2 17.2 .731 6 Nampok 4377 Dec. 64.1 56.3 7.8 .462 7 Chakoong 4407 May 83.9 76.2 7.7 .889 10 Singtam 4426 May 88.6 79.0 9.6 .969 5 Namten 4483 Dec. 64.8 58.3 6.5 .495 5 Purmiokshong 4521 Nov. 79.2 69.5 9.7 .715 2 Rungniok 4565 Jan. 66.5 59.7 16.8 .517 16 Singtam 4575 O.&N. 82.5 76.7 5.8 .901 6 Cheadam 4653 Dec. 70.2 55.0 15.2 .442 4 Sablakoo 4676 Dec. 72.9 65.7 7.2 .632 4 Bheti 4683 Nov. 78.3 66.1 12.2 .639 2 Temi 4771 May 81.2 74.1 7.1 .834 4 Lingtam 4805 May 80.0 73.8 6.2 .820 7 Khersiong 4813 Jan. 67.0 49.8 17.2 .370 6 Ditto 4813 March 77.1 70.5 6.6 .738 3 Tassiding 4840 Dec. 79.7 60.8 18.9 .538 6 Lingcham 4870 Dec. 78.5 71.8 6.7 .771 11 Dikkeeling 4952 Dec. 80.8 62.0 18.8 .559 9 Tehonpong 4978 Jan. 71.0 54.7 16.3 .439 --------------------------------------------------------------------- 137 Mean 76.5 66.8 9.7 .675

Humidity 0.837 Calcutta 0.730 Weight of vapour 4.33 gr. ,, 7.12 gr.

ELEVATION 5000 TO 6000 FEET.
EASTERN NEPAL AND SIKKIM.
No. of
Obs. Locality Elev. Month Tem. D.P. Diff. Tens
---------------------------------------------------------------------
4 Nampok 5075 May 65.8 60.8 5.0 .537
4 Tengling 5257 Jan. 44.7 39.1 5.6 .257
2 Choongtam, sunrise 5368 May 54.9 54.7 0.2 .438
7 ,, 9.50 a.m. ,, May 71.5 58.9 12.6 .504
5 ,, noon ,, May 71.0 59.4 11.6 .513
3 ,, 2.45 p.m. ,, May 66.4 59.4 7.0 .513
4 ,, 4 p.m. ,, May 63.5 59.2 4.3 .510
6 ,, sunset ,, May 61.4 60.5 0.9 .532
8 ,, 9.50 a.m. ,, Aug. 76.3 66.1 10.2 .640
8 ,, noon ,, Aug. 78.8 67.8 11.0 .677
7 ,, 2.40 p.m. ,, Aug. 72.9 66.5 6.4 .649
6 ,, 4 p.m. ,, Aug. 69.5 66.8 2.7 .655
8 ,, sunset ,, Aug. 66.9 65.4 1.5 .627
5 Salloobong 5277 Nov. 57.6 51.2 6.4 .390
6 Lingdam 5375 Dec. 44.3 43.0 1.3 .293
3 Makaroumbi 5485 Nov. 52.1 48.1 4.0 .350
8 Khabang 5505 Dec. 55.1 47.3 7.8 .340
6 Lingdam 5554 Dec. 45.0 43.7 1.3 .301
3 Yankutang 5564 Dec. 43.6 41.7 1.9 .280
4 Namtchi 5608 May 67.1 61.2 5.9 .544
6 Yoksun 5619 Jan. 42.7 34.0 8.7 .214
16 Ditto ,, Jan. 43.0 33.9 9.1 .213
2 Loongtoong 5677 Nov. 45.3 42.8 2.5 .292
4 Sakkiazong 5625 Nov. 54.1 50.9 3.2 .358
3 Phadong 8 a.m. 5946 Nov. 51.9 50.8 1.1 .383
3 ,, 9.50 a.m. ,, Nov. 55.9 53.0 2.9 .413
3 ,, noon ,, Nov. 60.7 56.5 4.2 .465
3 ,, 2.40 p.m. ,, Nov. 57.4 54.7 2.7 .438
2 ,, 4 p.m. ,, Nov. 55.5 52.8 2.7 .410
3 ,, sunset ,, Nov. 53.7 52.6 1.1 .408
3 Tumloong 5368 Nov. 64.2 62.6 1.6 .570
22 ,, 9.50 a.m. 5976) 54.1 50.0 4.1 .375
21 ,, noon ,, ) Nov. 57.3 51.7 5.6 .396
20 ,, 2.40 p.m. ,, _ and 57.3 51.4 5.9 .391
21 ,, 4 p.m. ,, ) Dec. 54.7 50.5 4.2 .380
21 ,, sunset ,, ) 51.8 48.5 3.3 .355
---------------------------------------------------------------------
260 Mean 57.7 53.3 4.5 .438

ELEVATION 5000 TO 6000 FEET.
CALCUTTA.
No. of
Obs. Locality Elev. Month Tem. D.P. Diff. Tens
---------------------------------------------------------------------
4 Nampok 5075 May 83.1 74.7 8.4 .845
4 Tengling 5257 Jan. 65.4 38.1 27.3 .247
2 Choongtam, sunrise 5368 May 78.2 73.9 4.3 .826
7 ,, 9.50 a.m. ,, May 89.8 80.0 19.8 1.000
5 ,, noon ,, May 92.7 79.9 12.8 .999
3 ,, 2.45 p.m. ,, May 95.4 78.7 16.7 .959
4 ,, 4 p.m. ,, May 93.6 79.0 14.6 .971
6 ,, sunset ,, May 89.1 77.1 12.0 .915
8 ,, 9.50 a.m. ,, Aug. 85.3 78.9 16.4 .967
8 ,, noon ,, Aug. 86.6 78.8 17.8 .965
7 ,, 2.40 p.m. ,, Aug. 86.4 78.8 7.6 .963
6 ,, 4 p.m. ,, Aug. 85.3 79.3 6.0 .980
8 ,, sunset ,, Aug. 83.6 78.5 5.1 .956
5 Salloobong 5277 Nov. 79.4 65.8 13.6 .634
6 Lingdam 5375 Dec. 68.8 59.9 8.9 .521
3 Makaroumbi 5485 Nov. 72.5 60.5 12.0 .532
8 Khabang 5505 Dec. 75.0 64.7 10.3 .611
6 Lingdam 5554 Dec. 71.0 56.5 14.5 .466
3 Yankutang 5564 Dec. 69.5 63.1 6.4 .579
4 Namtchi 5608 May 87.8 74.9 12.8 .850
6 Yoksun 5619 Jan. 68.2 58.1 10.1 .492
16 Ditto ,, Jan. 66.2 51.9 14.3 .399
2 Loongtoong 5677 Nov. 72.1 63.8 8.3 .595
4 Sakkiazong 5625 Nov. 78.3 66.1 12.2 .639
3 Phadong 8 a.m. 5946 Nov. 75.0 67.5 7.5 .670
3 ,, 9.50 a.m. ,, Nov. 80.9 67.9 13.0 .678
3 ,, noon ,, Nov. 85.6 64.8 20.8 .613
3 ,, 2.40 p.m. ,, Nov. 86.6 62.2 24.4 .562
2 ,, 4 p.m. ,, Nov. 85.5 61.9 23.6 .557
3 ,, sunset ,, Nov. 80.6 67.4 13.2 .667
3 Tumloong 5368 Nov. 83.8 77.5 6.3 .924
22 ,, 9.50 a.m. 5976) 75.1 61.9 13.2 .557
21 ,, noon ,, ) Nov. 79.7 60.1 19.6 .524
20 ,, 2.40 p.m. ,, _ and 81.3 58.0 23.3 .489
21 ,, 4 p.m. ,, ) Dec. 80.2 58.6 21.6 .499
21 ,, sunset ,, ) 76.7 61.2 15.5 .545
---------------------------------------------------------------------
260 Mean 77.6 67.8 9.8 .700

Humidity 0.865 Calcutta 0.730 Weight of vapour 4.70 gr. ,, 7.34 gr.

ELEVATION 6000 TO 7000 FEET. EASTERN NEPAL AND SIKKIM. No. of Obs. Locality Elev. Month Tem. D.P. Diff. Tens --------------------------------------------------------------------- 5 Runkpo 6008 Nov. 57.5 54.8 2.7 .440 11 Leebong 6021 Feb. 47.8 43.7 4.1 .300 11 Ditto ,, Jan. 47.8 43.4 4.4 .297 4 Dholep 6133 May 60.5 59.9 0.6 .520 2 Iwa River 6159 Dec. 41.2 40.5 0.7 .269 4 Dengha 6368 Aug. 66.7 64.0 2.7 .597 4 Kulhait River 6390 Dec. 41.9 41.9 0.0 .283 3 Latong 6391 Oct. 54.0 53.2 0.8 .416 1 Doobdi 6472 Jan. 46.6 36.2 10.4 .231 10 Pemiongchi 6584 Jan. 40.7 35.8 4.9 .228 4 Keadom 6609 Aug. 63.5 60.0 3.5 .523 6 Hee-hill 6677 Jan. 40.8 34.1 6.7 .215 7 Dumpook 6678 Jan. 40.2 31.8 8.4 .198 4 Changachelling 6828 Jan. 50.6 31.8 18.8 .198 --------------------------------------------------------------------- 76 Mean 50.0 45.1 4.9 .337

CALCUTTA. No. of Obs. Locality Elev. Month Tem. D.P. Diff. Tens --------------------------------------------------------------------- 5 Runkpo 6008 Nov. 79.5 73.4 6.1 .810 11 Leebong 6021 Feb. 74.9 59.7 15.2 .517 11 Ditto ,, Jan. 66.9 56.2 10.7 .460 4 Dholep 6133 May 89.4 81.4 8.0 .046 2 Iwa River 6159 Dec. 69.6 60.2 9.4 .527 4 Dengha 6368 Aug. 86.1 78.8 7.3 .962 4 Kulhait River 6390 Dec. 71.3 60.9 10.4 .539 3 Latong 6391 Oct. 55.5 44.1 11.4 .305 1 Doobdi 6472 Jan. 78.7 58.0 20.7 .490 10 Pemiongchi 6584 Jan. 66.3 54.4 11.9 .434 4 Keadom 6609 Aug. 79.7 77.5 2.2 .925 6 Hee-hill 6677 Jan. 64.0 58.0 6.0 .489 7 Dumpook 6678 Jan. 68.5 53.8 14.7 .426 4 Changachelling 6828 Jan. 68.3 53.6 14.8 .423 --------------------------------------------------------------------- 76 Mean 72.8 62.1 10.6 .597

Humidity 0.845 Calcutta 0.701 Weight of vapour 3.60 gr. ,, 6.11 gr.

ELEVATION 7000 TO 8000 FEET. EASTERN NEPAL AND SIKKIM. No. of Obs. Locality Elev. Month Tem. D.P. Diff. Tens --------------------------------------------------------------------- 1 Pemiongchi 7083 Jan. 46.2 33.5 12.7 .210 2 Goong 7216 Nov. 49.0 48.5 0.5 .355 8 Kampo-Samdong 7329 May/ 59.1 58.2 0.9 .493 Aug. 1 Hee-hill 7289 Jan. 51.3 26.4 24.9 .163 1 Ratong river 7143 Jan. 36.5 25.3 11.2 .157 4 Source of Balasun 7436 Oct. 48.3 48.3 0.0 .352 8 Goong ridge 7441 Oct. 51.2 50.2 1.0 .376 --------------------------------------------------------------------- 25 Dorjiling Mean 48.8 41.5 7.3 .301

CALCUTTA. No. of Obs. Locality Elev. Month Tem. D.P. Diff. Tens --------------------------------------------------------------------- 1 Pemiongchi 7083 Jan. 76.8 51.8 25.0 .396 2 Goong 7216 Nov. 79.7 69.1 10.6 .705 8 Kampo-Samdong 7329 May/ 83.6 77.4 6.2 .922 Aug. 1 Hee-hill 7289 Jan. 72.8 56.6 16.2 .466 1 Ratong river 7143 Jan. 60.0 52.9 17.1 .412 4 Source of Balasun 7436 Oct. 81.2 73.7 7.5 .819 8 Goong ridge 7441 Oct. 80.7 66.9 13.8 .657 --------------------------------------------------------------------- 25 Dorjiling Mean 76.4 64.1 12.3 .625

From mean of above and Dorjiling: Humidity 0.826 Calcutta 0.668 Weight of vapour 3.85 gr. ,, 7.28 gr.

ELEVATION 8000 TO 9000 FEET.
EASTERN NEPAL AND SIKKIM.
No. of
Obs. Locality Elev. Month Tem. D.P. Diff. Tens
---------------------------------------------------------------------
4 Sinchul 8607 Jan. 41.7 34.3 7.4 .216
2 Ditto ,, April 66.8 44.6 22.2 .310
1 Ascent of Tonglo 8148 May 56.2 54.4 1.8 .434
2 Tambur river 8081 Nov. 38.0 33.9 4.1 .213
3 Sakkiazong 8353 Nov. 49.7 37.4 12.3 .241
4 Chateng 8418 Oct. 43.8 43.2 0.6 .299
6 Buckim 8659 Jan. 30.2 22.8 7.4 .143
9 Ditto ,, Jan. 33.9 33.1 0.8 .207
1 Chateng 8752 May 67.2 60.7 6.5 .536
11 Lachoong 7 a.m. 8777) 53.3 51.1 2.2 .388
12 ,, 9.50 a.m. ,, ) 60.2 55.3 4.9 .447
7 ,, noon ,, ) Aug. 61.6 57.1 4.5 .475
4 ,, 2.40 p.m. ,, _ and 58.1 56.4 1.7 .464
7 ,, 4 p.m. ,, ) Oct. 58.6 53.8 4.8 .424
10 ,, sunset ,, ) 55.5 54.3 1.2 .432
12 ,, Miscellaneous ,, ) 55.9 49.6 6.3 .368
10 Lamteng 6 a.m. 8884) May 53.9 52.0 1.9 .400
10 ,, 9.50 a.m. ,, ) June 62.8 56.2 6.6 .461
4 ,, noon ,, _ July 62.8 56.2 6.6 .461
5 ,, 2.40 p.m. ,, ) and 58.3 54.5 3.9 .435
6 ,, 4 p.m. ,, ) Aug. 56.2 54.7 1.5 .438
8 ,, sunset ,, ) 53.3 52.5 0.8 .407
11 Zemu Sundong 7 a.m. 8976) 55.7 55.3 0.4 .448
11 ,, 9.50 a.m. ,, ) June 59.7 52.8 6.9 .412
7 ,, noon ,, ) and 63.1 57.1 6.0 .473
6 ,, 2.40 p.m. ,, _ July 61.0 58.6 2.4 .500
8 ,, sunset ,, ) 57.9 56.1 1.8 .459
10 ,, 4 p.m. ,, ) 53.8 52.6 1.2 .407
1 Goong 8999 Nov. 49.0 48.5 0.5 .355
1 Tendong (top) 8663 May 55.5 50.0 5.5 .373
---------------------------------------------------------------------
193 Mean 54.5 50.0 4.5 .388

CALCUTTA.
No. of
Obs. Locality Elev. Month Tem. D.P. Diff. Tens
---------------------------------------------------------------------
4 Sinchul 8607 Jan. 66.3 56.9 9.4 .472
2 Ditto ,, April 96.9 75.4 21.5 .866
1 Ascent of Tonglo 8148 May 86.8 78.9 7.9 .967
2 Tambur river 8081 Nov. 71.7 64.1 7.6 .599
3 Sakkiazong 8353 Nov. 74.0 62.4 11.6 .566
4 Chateng 8418 Oct. 79.2 77.5 1.7 .926
6 Buckim 8659 Jan. 68.6 49.4 19.2 .366
9 Ditto ,, Jan. 69.8 52.2 17.6 .403
1 Chateng 8752 May 89.7 76.8 12.9 .904
11 Lachoong 7 a.m. 8777) 83.0 78.9 4.1 .967
12 ,, 9.50 a.m. ,, ) 87.1 79.9 7.2 .999
7 ,, noon ,, ) Aug. 90.1 79.4 10.7 .983
4 ,, 2.40 p.m. ,, _ and 88.0 80.0 8.0 1.007
7 ,, 4 p.m. ,, ) Oct. 87.5 79.4 8.1 .981
10 ,, sunset ,, ) 84.5 78.7 5.8 .959
12 ,, Miscellaneous ,, ) 85.9 75.2 10.7 .858
10 Lamteng 6 a.m. 8884) May 59.5 56.4 3.1 .464
10 ,, 9.50 a.m. ,, ) June 88.3 78.7 9.6 .959
4 ,, noon ,, ) July 92.0 78.0 14.0 .939
5 ,, 2.40 p.m. ,, _ and 92.2 78.4 13.8 .950
6 ,, 4 p.m. ,, ) Aug. 92.3 77.1 15.2 .914
8 ,, sunset ,, ) 88.1 77.4 10.7 .922
11 Zemu Sundong 7 a.m. 8976) 80.4 79.8 0.6 .997
11 ,, 9.50 a.m. ,, ) June 86.3 79.0 7.3 .969
7 ,, noon ,, _ and 88.0 79.8 8.2 .994
6 ,, 2.40 p.m. ,, ) July 89.6 78.2 11.4 .944
8 ,, sunset ,, ) 89.3 79.0 10.3 .970
10 ,, 4 p.m. ,, ) 82.7 77.3 5.4 .920
1 Goong 8999 Nov. 79.7 69.1 10.6 .705
1 Tendong (top) 8663 May 88.6 78.1 10.5 .943
---------------------------------------------------------------------
193 Mean 83.7 73.7 9.8 .847

Humidity 0.858 Calcutta 0.730 Weight of vapour 4.23 gr. ,, 8.75 gr.

ELEVATION 9000 TO 10,000 FEET. EASTERN NEPAL AND SIKKIM. No. of Obs. Locality Elev. Month Tem. D.P. Diff. Tens --------------------------------------------------------------------- 4 Yangma Guola 9279 Nov. 37.8 33.1 4.7 .207 8 Nanki 9320 Nov. 42.3 38.2 4.0 .249 4 Singalelah 9295 Dec. 36.2 35.7 0.5 .227 1 Sakkiazong 9322 Nov. 53.5 33.3 20.2 .209 1 Zemu river 9828 June 60.0 47.6 12.4 .343 --------------------------------------------------------------------- 18 Mean 46.0 37.6 8.4 .247

CALCUTTA. No. of Obs. Locality Elev. Month Tem. D.P. Diff. Tens --------------------------------------------------------------------- 4 Yangma Guola 9279 Nov. 72.7 61.4 11.3 .549 8 Nanki 9320 Nov. 52.2 48.3 3.9 .352 4 Singalelah 9295 Dec. 70.9 62.1 8.8 .560 1 Sakkiazong 9322 Nov. 80.0 57.3 22.7 .478 1 Zemu river 9828 June 93.3 81.9 11.4 1.062 --------------------------------------------------------------------- 18 Mean 73.8 62.2 11.6 .600

Humidity 0.860 Calcutta 0.760 Weight of vapour 3.46 gr. ,, 9.00 gr.

ELEVATION 10,000 TO 11,000 FEET.
EASTERN NEPAL AND SIKKIM.
No. of
Obs. Locality Elev. Month Tem. D.P. Diff. Tens
---------------------------------------------------------------------
13 Tonglo 10,008 May 51.5 50.2 1.3 .376
3 Nanki 10,024 Nov. 42.8 35.5 7.3 .225
4 Yalloong river 10,058 Dec. 37.7 29.6 8.1 .183
2 Tonglo top 10,079 May 49.9 47.9 2.0 .348
2 Yeunga 10,196 Oct. 45.9 44.7 1.2 .311
4 Zemu river 10,247 June 45.4 44.2 1.2 .306
10 Wallanchoon 10,348 Nov. 37.9 30.2 7.7 .187
4 Laghep 10,423 Nov. 46.0 42.4 3.6 .287
3 Ditto ,, Nov. 37.6 37.0 0.6 .238
16 Thlonok river 7 a.m. 10,846 June 48.5 47.2 1.3 .339
17 ,, 9.50 a.m. ,, June 57.6 51.4 6.2 .392
9 ,, noon ,, June 56.1 50.6 5.5 .382
8 ,, 2.40 p.m. ,, June 54.8 50.6 4.2 .381
9 ,, 4 p.m. ,, June 53.4 50.6 2.8 .381
15 ,, sunset ,, June 49.8 48.9 0.9 .359
4 Yangma Valley 10,999 Dec. 31.6 24.3 7.3 .149
---------------------------------------------------------------------
123 Mean 46.7 42.8 3.8 .303

CALCUTTA.
No. of
Obs. Locality Elev. Month Tem. D.P. Diff. Tens
---------------------------------------------------------------------
13 Tonglo 10,008 May 88.8 80.8 8.0 1.030
3 Nanki 10,024 Nov. 79.5 65.8 13.7 .633
4 Yalloong river 10,058 Dec. 77.7 62.1 15.6 .560
2 Tonglo top 10,079 May 89.4 80.5 8.9 1.018
2 Yeunga 10,196 Oct. 79.5 77.1 2.4 .915
4 Zemu river 10,247 June 84.6 75.1 9.5 .856
10 Wallanchoon 10,348 Nov. 76.5 61.9 14.6 .558
4 Laghep 10,423 Nov. 80.9 68.0 12.9 .681
3 Ditto ,, Nov. 75.3 69.4 5.9 .712
16 Thlonok river 7 a.m. 10,846 June 79.0 75.1 3.9 .856
17 ,, 9.50 a.m. ,, June 87.4 78.8 8.6 .965
9 ,, noon ,, June 90.0 79.3 10.7 .979
8 ,, 2.40 p.m. ,, June 88.5 79.7 8.8 .991
9 ,, 4 p.m. ,, June 88.7 78.7 10.0 .962
15 ,, sunset ,, June 85.5 78.0 7.5 .938
4 Yangma Valley 10,999 Dec. 74.4 61.9 12.3 .558
---------------------------------------------------------------------
123 Mean 82.8 73.3 9.5 .826

Humidity 0.878 Calcutta 0.740 Weight of vapour 3.35 gr. ,, 8.70 gr.

ELEVATION 11,000 TO 12,000 FEET.
EASTERN NEPAL AND SIKKIM.
No. of
Obs. Locality Elev. Month Tem. D.P. Diff. Tens
---------------------------------------------------------------------
3 Barfonchen 11,233 Nov. 36.8 31.9 4.9 .198
3 Punying 11,299 Aug. 50.2 49.5 0.7 .367
1 Kambachen village 11,378 Dec. 43.3 32.5 10.8 .203
12 Tallum 7 a.m. 11,482 July 50.4 47.8 2.6 .347
6 ,, 9.50 a.m. ,, July 58.1 50.5 7.6 .380
8 ,, noon ,, July 57.9 50.8 7.1 .384
5 ,, 2.40 p.m. ,, July 55.7 50.2 5.5 .377
6 ,, 4 p.m. ,, July 54.3 50.1 4.2 .375
6 ,, sunset ,, July 48.8 47.3 1.5 .340
2 Kambachen valley 11,484 Dec. 30.4 26.0 4.4 .161
10 Yeumtong 7 a.m. 11,887) 44.4 43.8 0.6 .302
9 ,, 9.50 a.m. ,, ) Aug. 53.6 48.9 4.7 .360
5 ,, noon ,, ) Sep. 54.5 48.3 6.2 .353
7 ,, 2.40 p.m. ,, _ and 48.8 47.4 1.4 .342
4 ,, 4 p.m. ,, ) Oct. 48.4 47.1 1.3 .338
10 ,, sunset ,, ) 42.0 35.9 6.1 .229
7 ,, Miscellaneous ,, Oct. 43.5 37.1 6.4 .239
---------------------------------------------------------------------
104 Mean 48.3 43.8 4.5 .311

CALCUTTA.
No. of
Obs. Locality Elev. Month Tem. D.P. Diff. Tens
---------------------------------------------------------------------
3 Barfonchen 11,233 Nov. 76.3 69.6 6.7 .719
3 Punying 11,299 Aug. 84.5 78.8 5.7 .963
1 Kambachen village 11,378 Dec. 80.0 61.2 18.8 .544
12 Tallum 7 a.m. 11,482 July 85.0 80.3 4.7 1.010
6 ,, 9.50 a.m. ,, July 88.1 79.7 8.4 .993
8 ,, noon ,, July 89.7 81.3 8.4 1.043
5 ,, 2.40 p.m. ,, July 89.3 80.6 8.7 1.020
6 ,, 4 p.m. ,, July 90.3 79.4 10.9 .981
6 ,, sunset ,, July 86.6 80.0 6.6 1.001
2 Kambachen valley 11,484 Dec. 69.9 59.5 10.4 .515
10 Yeumtong 7 a.m. 11,887) 83.0 78.9 4.1 .967
9 ,, 9.50 a.m. ,, ) Aug. 87.5 78.7 8.8 .959
5 ,, noon ,, ) Sep. 89.7 77.2 12.5 .917
7 ,, 2.40 p.m. ,, _ and 87.2 77.2 10.0 .915
4 ,, 4 p.m. ,, ) Oct. 85.2 77.8 7.4 .934
10 ,, sunset ,, ) 60.6 58.5 2.1 .497
7 ,, Miscellaneous ,, Oct. 83.7 69.7 14.0 .720
---------------------------------------------------------------------
104 Mean 83.3 74.6 8.7 .865

Humidity 0.860 Calcutta 0.760 Weight of vapour 3.46 gr. ,, 9.00 gr.

ELEVATION 12,000 TO 13,000 FEET.
EASTERN NEPAL AND SIKKIM.
No. of
Obs. Locality Elev. Month Tem. D.P. Diff. Tens
---------------------------------------------------------------------
9 Zemu river 7 a.m. 12,070) 46.6 45.6 1.0 .321
9 ,, 9.50 a.m. ,, ) June 51.1 49.0 2.1 .362
7 ,, noon ,, _ and 51.1 50.2 0.9 .376
7 ,, 2.40 p.m. ,, ) July 51.2 50.3 0.9 .377
7 ,, 4 p.m. ,, ) 49.7 48.9 0.8 .360
8 ,, sunset ,, ) 48.1 47.6 0.5 .344
2 Yangma Valley 12,129 Nov. 34.8 22.7 12.1 .143
1 Zemu river 12,422 June 49.0 46.6 2.4 .332
3 Chumanako 12,590 Nov. 37.3 28.3 9.0 .174
7 Tungu 7 a.m. 12,751 July 45.1 44.1 1.0 .305
5 ,, 9.50 a.m. ,, July 53.1 48.6 4.5 .355
1 ,, noon ,, July 62.3 52.7 9.6 .409
1 ,, 2.40 p.m. ,, July 60.0 53.8 6.2 .425
6 ,, sunset ,, July 46.4 45.3 1.1 .317
3 ,, sunrise ,, Oct. 38.2 35.0 3.2 .222
4 ,, 9.50 a.m. ,, Oct. 46.5 42.8 3.7 .292
4 ,, noon ,, Oct. 46.1 42.0 4.1 .284
4 ,, 2.40 p.m. ,, Oct. 43.8 42.1 1.7 .285
4 ,, 4 p.m. ,, Oct. 42.3 40.8 1.5 .271
6 ,, sunset ,, Oct. 41.0 38.7 2.3 .253
23 ,, Miscellaneous ,, Oct. 43.2 40.8 2.4 .272
13 ,, Ditto ,, July 51.3 47.4 3.6 .345
6 Tuquoroma 12,944 Nov. 26.0 23.4 2.6 .146
---------------------------------------------------------------------
140 Mean 46.3 42.9 3.4 .303

CALCUTTA.
No. of
Obs. Locality Elev. Month Tem. D.P. Diff. Tens
---------------------------------------------------------------------
9 Zemu river 7 a.m. 12,070) 80.6 77.7 2.9 .931
9 ,, 9.50 a.m. ,, ) June 84.5 75.1 9.4 .972
7 ,, noon ,, _ and 87.0 82.2 4.8 1.074
7 ,, 2.40 p.m. ,, ) July 86.3 80.0 6.3 1.000
7 ,, 4 p.m. ,, ) 86.5 80.2 6.3 1.006
8 ,, sunset ,, ) 81.4 77.5 3.9 .926
2 Yangma Valley 12,129 Nov. 70.6 63.7 16.9 .592
1 Zemu river 12,422 June 93.2 79.6 13.6 .989
3 Chumanako 12,590 Nov. 75.1 73.8 1.3 .822
7 Tungu 7 a.m. 12,751 July 80.5 78.3 2.2 .949
5 ,, 9.50 a.m. ,, July 87.1 79.4 7.7 .982
1 ,, noon ,, July 88.9 77.8 11.1 .935
1 ,, 2.40 p.m. ,, July 85.3 79.5 5.8 .985
6 ,, sunset ,, July 84.7 79.1 5.6 .974
3 ,, sunrise ,, Oct. 79.4 77.8 1.6 .932
4 ,, 9.50 a.m. ,, Oct. 85.0 78.6 6.4 .957
4 ,, noon ,, Oct. 85.0 78.2 6.8 .944
4 ,, 2.40 p.m. ,, Oct. 86.4 78.8 7.6 .963
4 ,, 4 p.m. ,, Oct. 85.9 78.5 7.4 .956
6 ,, sunset ,, Oct. 83.3 78.2 5.1 .947
23 ,, Miscellaneous ,, Oct. 84.5 78.4 6.1 .950
13 ,, Ditto ,, July 85.7 79.0 6.7 .971
6 Tuquoroma 12,944 Nov. 75.1 60.8 14.3 .537
---------------------------------------------------------------------
140 Mean 83.6 77.1 6.5 .926

Humidity 0.890 Calcutta 0.815 Weight of vapour 3.37 gr. ,, 9.75 gr.

ELEVATION 13,000 TO 14,000 FEET. EASTERN NEPAL AND SIKKIM. No. of Obs. Locality Elev. Month Tem. D.P. Diff. Tens --------------------------------------------------------------------- 7 Mon Lepcha 13,090 Jan. 27.1 18.5 8.6 .122 4 Ditto 13,073 Jan. 25.6 16.4 9.2 .113 2 Tunkra valley 13,111 Aug. 45.0 43.5 1.5 .298 21 Jongri 13,194 Jan. 22.7 10.5 12.2 .091 1 Zemu river 13,281 June 46.7 46.7 0.0 .334 4 Choonjerma 13,288 Dec. 39.0 11.1 27.9 .093 10 Yangma village 13,502 Nov./ 33.8 18.6 15.2 .123 Dec. 1 Wallanchoon road 13,505 Nov. 28.0 9.5 18.5 .088 3 Kambachen, below pass 13,600 Dec. 40.0 18.6 21.4 .123 --------------------------------------------------------------------- 53 Mean 34.2 21.5 12.6 .154

CALCUTTA. No. of Obs. Locality Elev. Month Tem. D.P. Diff. Tens --------------------------------------------------------------------- 7 Mon Lepcha 13,090 Jan. 70.0 50.8 19.2 .527 4 Ditto 13,073 Jan. 71.7 49.9 21.8 .373 2 Tunkra valley 13,111 Aug. 81.2 78.7 2.5 .962 21 Jongri 13,194 Jan. 70.6 53.2 17.4 .417 1 Zemu river 13,281 June 92.9 86.6 6.2 1.230 4 Choonjerma 13,288 Dec. 69.8 61.8 28.0 .555 10 Yangma village 13,502 Nov./ 78.9 62.1 16.8 .561 Dec. 1 Wallanchoon road 13,505 Nov. 66.4 61.8 14.6 .555 3 Kambachen, below pass 13,600 Dec. 72.9 62.2 10.7 .563 --------------------------------------------------------------------- 53 Mean 74.9 63.0 11.9 .636

Humidity 0.634 Calcutta 0.678 Weight of vapour 1.61 gr. 6.28 gr.

ELEVATION 15,000 TO 16,000 FEET. EASTERN NEPAL AND SIKKIM. No. of Obs. Locality Elev. Month Tem. D.P. Diff. Tens --------------------------------------------------------------------- 1 Yangma valley 15,186 Dec. 42.2 20.7 21.5 .133 1 Choonjerma pass 15,259 Dec. 34.3 10.5 23.8 .091 8 Lachee-pia 15,262 Aug. 42.0 41.6 0.4 .279 12 Momay, 7 a.m. ,, Sept. 39.4 34.7 4.7 .219 6 ,, 9.50 a.m. ,, Sept. 50.9 41.7 9.2 .280 4 ,, noon ,, Sept. 51.7 43.6 8.1 .299 8 ,, 2.40 p.m. ,, Sept. 49.7 41.9 7.8 .283 10 ,, 4 p.m. ,, Sept. 44.4 41.3 3.1 .276 16 ,, sunset ,, Sept. 41.5 38.6 2.9 .252 8 ,, Miscellaneous ,, Sept. 47.6 41.4 6.2 .277 6 ,, ,, ,, Oct. 40.9 36.5 4.4 .234 3 Sittong 15,372 Oct. 38.6 29.8 8.8 .184 2 Palung 15,676 Oct. 44.6 39.8 4.8 .262 1 Kambachen pass 15,770 Dec. 26.5 15.9 10.6 .111 1 Yeumtong 15,985 Sept. 44.6 43.7 0.9 .300 --------------------------------------------------------------------- 87 Mean 42.6 34.8 7.8 .232

CALCUTTA. No. of Obs. Locality Elev. Month Tem. D.P. Diff. Tens --------------------------------------------------------------------- 1 Yangma valley 15,186 Dec. 80.8 62.0 18.8 .559 1 Choonjerma pass 15,259 Dec. 77.9 60.6 17.3 .534 8 Lachee-pia 15,262 Aug. 85.5 79.4 6.1 .982 12 Momay, 7 a.m. ,, Sept. 80.5 78.8 1.7 .966 6 ,, 9.50 a.m. ,, Sept. 87.6 78.8 8.8 .963 4 ,, noon ,, Sept. 89.5 79.7 9.8 .990 8 ,, 2.40 p.m. ,, Sept. 90.0 78.3 11.7 .949 10 ,, 4 p.m. ,, Sept. 88.7 77.6 11.1 .928 16 ,, sunset ,, Sept. 84.2 78.4 5.8 .952 8 ,, Miscellaneous ,, Sept. 87.4 78.6 8.8 .956 6 ,, ,, ,, Oct. 83.9 69.3 14.6 .710 3 Sittong 15,372 Oct. 84.0 77.5 6.5 .926 2 Palung 15,676 Oct. 86.8 78.5 8.3 .954 1 Kambachen pass 15,770 Dec. 78.0 58.5 19.5 .498 1 Yeumtong 15,985 Sept. 88.8 80.5 8.3 1.016 --------------------------------------------------------------------- 87 Mean 84.9 74.4 10.5 .859

Humidity 0.763 Calcutta 0.719 Weight of vapour 2.55 gr. 8.95 gr.

ELEVATION 16,000 TO 17,000 FEET. EASTERN NEPAL AND SIKKIM. No. of Obs. Locality Elev. Month Tem. D.P. Diff. Tens --------------------------------------------------------------------- 1 Kanglachem pass 16,038 Dec. 32.8 16.3 16.5 .110 3 Tunkra pass 16,038 Aug. 39.8 38.7 1.1 .252 1 Wallanchoon pass 16,756 Nov. 18.0 -6.0 24.0 .046 5 Teumtso 16,808 Oct. 32.4 25.1 7.3 .156 6 Cholamoo lake 16,900 Oct. 31.4 20.2 11.2 .130 1 Donkia mountain 16,978 Sept. 40.2 25.9 14.3 .160 --------------------------------------------------------------------- 17 Mean 32.4 20.0 12.4 .142

CALCUTTA. No. of Obs. Locality Elev. Month Tem. D.P. Diff. Tens --------------------------------------------------------------------- 1 Kanglachem pass 16,038 Dec. 80.7 61.1 19.6 .543 3 Tunkra pass 16,038 Aug. 86.0 78.7 7.3 .959 1 Wallanchoon pass 16,756 Nov. 79.9 57.6 22.3 .483 5 Teumtso 16,808 Oct. 85.0 75.7 9.3 .872 6 Cholamoo lake 16,900 Oct. 79.8 68.4 11.4 .690 1 Donkia mountain 16,978 Sept. 87.6 78.8 18.8 .963 --------------------------------------------------------------------- 17 Mean 83.2 70.1 13.3 .752

Humidity 0.640 Calcutta 0.658 Weight of vapour 1.53 gr. 7.80 gr.

ELEVATION 17,000 TO 18,500 FEET. EASTERN NEPAL AND SIKKIM. No. of Obs. Locality Elev. Month Tem. D.P. Diff. Tens --------------------------------------------------------------------- 1 Kinchinjhow 17,624 Sept. 47.5 30.9 16.6 .191 1 Sebolah pass 17,585 Sept. 46.5 34.6 11.9 .218 1 Donkin mountain 18,307 Sept. 38.8 35.3 3.5 .224 3 Bhomtso 18,450 Oct. 54.0 4.4 49.6 .072 2 Donkia pass 18,466 Sept. 41.8 30.3 11.5 .188 2 Ditto 18,466 Oct. 40.1 25.0 15.1 .155 --------------------------------------------------------------------- 10 Mean 44.8 26.8 18.0 .175

CALCUTTA. No. of Obs. Locality Elev. Month Tem. D.P. Diff. Tens --------------------------------------------------------------------- 1 Kinchinjhow 17,624 Sept. 85.7 79.7 16.0 .991 1 Sebolah pass 17,585 Sept. 88.8 80.0 18.8 1.002 1 Donkin mountain 18,307 Sept. 90.7 79.3 11.4 .981 3 Bhomtso 18,450 Oct. 91.1 61.1 20.0 .543 2 Donkia pass 18,466 Sept. 84.1 78.4 15.7 .950 2 Ditto 18,466 Oct. 86.5 65.5 21.0 .627 --------------------------------------------------------------------- 10 Mean 87.8 74.0 12.2 .849

Humidity 0.532 Calcutta 0.648 Weight of vapour 1.90 gr. 8.78 gr.

SUMMARY.

HUMIDITY WEIGHT OF VAPOUR No. of Elevations Sta- Sik- Cal- Diff. Sik- Cal- Diff. Obs. in Feet tions kim cutta Sikkim kim cutta Sikkim ---------------------------------------------------------------------- 48 735 to 2000 9 .717 .663 +.054 5.57 6.88 -1.31 49 2000 to 3000 9 .820 .740 .080 5.45 7.13 1.68 48 3000 to 4000 13 .858 .732 .116 4.23 6.60 2.37 137 4000 to 5000 23 .837 .730 .107 4.33 7.12 2.79 260 5000 to 6000 15 .865 .730 .135 4.70 7.34 2.64 76 6000 to 7000 13 .845 .701 .144 3.60 6.71 3.11 1023 7000 to 8000 14 .826 .668 .158 3.85 7.28 3.43 193 8000 to 9000 13 .858 .730 .128 4.23 8.75 4.52 18 9000 to 10,000 5 .747 .724 .023 2.80 6.28 3.48 123 10,000 to 11,000 10 .878 .740 .138 3.35 8.70 4.35 104 11,000 to 12,000 6 .860 .760 .100 3.46 9.00 5.54 140 12,000 to 13,000 6 .890 .815 .075 3.37 9.75 6.38 53 13,000 to 14,000 9 .634 .678 -.044 1.61 6.28 4.67 87 15,000 to 16,000 8 .763 .719 +.044 2.55 8.95 6.40 17 16,000 to 17,000 6 .640 .658 .018 1.53 7.80 6.27 10 17,000 to 18,500 5 .532 .648 -.116 1.90 8.78 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,OOQ 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.* [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._

Elev. No. above TEMP. D.P. TENSION SAT. of sea. Obs. Locality Feet C. T. C. T. C. T. C. T. --------------------------------------------------------------------- 4 Rummai 293 82.2 70.6 61.7 60.5 .553 .532 .517 .717 4 Belakoba 368 92.8 85.5 62.6 63.0 .570 .578 .382 .485 3 Rangamally 275 84.2 75.0 68.7 62.5 .695 .568 .605 .665 3 Bhojepore 404 90.1 81.2 54.1 44.3 .429 .308 .313 .295 4 Thakyagunj 284 84.9 77.1 61.3 60.8 .547 .537 .466 .588 3 Bhatgong 225 87.4 74.9 64.7 54.6 .611 .436 .480 .512 2 Sahigunj 231 80.2 68.0 66.2 53.1 .642 .414 .635 .409 8 Titalya 362 85.5 80.0 55.4 56.1 .448 .459 .376 .459 --------------------------------------------------------------------- 31 Means 305 85.9 79.0 61.8 56.9 .562 .479 .472 .516 May, 1850 ) 131 89.7 K78.6 76.7 K71.4 .904 K.759 .665 K.793 Kishengunj) --------------------------------------------------------------------- Vapour in a cubic foot--Kishengunj 8.20 Terai 5.08 Calcutta 9.52 Calcutta 5.90 Mean difference of temperature between Terai and Calcutta, from 31 observations in March, as above, excluding minima Terai--6.9 Mean difference from 26 observations in March, including minima Terai--9.7 Mean difference of temperature at Siligore on May 1, 1850-- 10.9 Mean difference of temperature at Kishengunj on May 1, 1850-- 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 degrees north of Calcutta, is at least 6 degrees or 7 degrees 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."