Books: Himalayan Journals (Complete)

J >> J. D. Hooker >> Himalayan Journals (Complete)

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Number Difference Equivalent
Month of Observ. of Temperature 1 degree F.=
-------------------------------------------------------------
January 27 30.4 287 ft.
February 84 32.8 265
March 37 41.9 196
April 7 36.0 236
March and April 29 37.3 224
July 83 23.6 389
August 74 22.4 415
September 95 25.7 350
October 18 29.5 297
-------------------------------------------------------------
Sum 454 Mean 31.1 Mean 296 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 degree 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._

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

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

V.--_Miscellaneous observations (chiefy 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._

Number of Number of Equivalent
Elevation Stations Observations 1 degree F.=
---------------------------------------------------------------
1,000 to 4,000 ft. 10 45 422 ft.
4,000 to 8,000 ft. 21 283 336
8,000 to 12,000 ft. 18 343 355
12,000 to 17,000 ft. 29 219 417
---------------------------------------------------------------
Sum 78 Sum 890 Mean 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 degree=348 ft.
At 17 stations lower in elevation 1 degree=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 degree=322 feet.

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 February and March
Upper Stations Jillapahar, 7,430 feet
Lower Stations Leebong, 6000 feet
1 degree= 269 feet

Month February
Upper Stations Jillapahar, 7,430 feet
Lower Stations Guard-house, Great Rungeet, 1,864 feet
1 degree= 298 feet

Month April
Upper Stations Leebong, 6000 feet
Lower Stations Guard-house, Great Rungeet, 1,864 feet
1 degree= 297 feet

Month April
Upper Stations Jillapahar, 7,430 feet
Lower Stations Khersiong, 4,813 feet
1 degree= 297 feet

Month March and April
Upper Stations Khersiong, 4,813 feet
Lower Stations Punkabaree, 1,850 feet
1 degree= 223 feet

Month March, April, May
Upper Stations Jillapahar, 7,430 feet
Lower Stations Punkabaree, 1,850 feet
1 degree= 253 feet

Mean 1 degree=273 feet

The above results would seem to indicate that up to an elevation
of 7,500 feet, the temperature diminishes rather more than 1 degree
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 degree=300 feet, for elevations from 1000 to 8000 feet.
1 degree=320 feet, for elevations from 8000 to 10,000 feet.
1 degree=350 feet, for elevations from 10,000 to 14,000 feet.
1 degree=400 feet, for elevations from 14,000 to 18,000 feet.

VIII.--_Khasia mountain observations._

Churra Poonji
Date June 13 to 26
Calcutta Observations 86.3 degrees
Number of Observations 63
Churra Observations 70.1 degrees
Number of Observations 67
1 degree= 300 feet
Altitude above the Sea 4,069 feet

Date August 7 to September 4
Calcutta Observations 84.6 degrees
Number of Observations 196
Churra Observations 69.2 degrees
Number of Observations 214
1 degree= 331 feet
Altitude above the Sea 4,225 feet

Date October 29 to November 16
Calcutta Observations 80.7 degrees
Number of Observations 85
Churra Observations 63.1 degrees
Number of Observations 133
1 degree= 282 feet
Altitude above the Sea 4,225 feet

Total Calcutta Observations 354
Total Churra Observations 414
Mean 1 degree= 304 feet

Kala-panee
Date June, Aug., Sept.
Calcutta Observations 85.5 degrees
Number of Observations 35
Khasia Observations 67.4 degrees
Number of Observations 35
1 degree= 345 feet
Altitude above the Sea 5,302 feet

Moflong
Date June, July, Aug., Oct.
Calcutta Observations 85.9 degrees
Number of Observations 73
Khasia Observations 68.8 degrees
Number of Observations 74
1 degree= 373 feet
Altitude above the Sea 6,062 feet

Syong
Date
Calcutta Observations 85.1 degrees
Number of Observations 4
Khasia Observations 65.0 degrees
Number of Observations 6
1 degree= 332 feet
Altitude above the Sea 5,734 feet

Myrung
Date August
Calcutta Observations 89.1 degrees
Number of Observations 42
Khasia Observations 69.7 degrees
Number of Observations 41
1 degree= 343 feet
Altitude above the Sea 5,632 feet

Myrung
Date October
Calcutta Observations 82.9 degrees
Number of Observations 21
Khasia Observations 63.2 degrees
Number of Observations 58
1 degree= 336 feet
Altitude above the Sea 5,632 feet

Nunklow
Calcutta Observations 86.4 degrees
Number of Observations 139
Khasia Observations 70.9 degrees
Number of Observations 139
1 degree= 372 feet
Altitude above the Sea 4,688 feet

Mooshye
Date September 23
Calcutta Observations 78.5 degrees
Number of Observations 9
Khasia Observations 66.3 degrees
Number of Observations 12
1 degree= 499 feet
Altitude above the Sea 4,863 feet

Pomrang
Date September 23
Calcutta Observations 82.7 degrees
Number of Observations 51
Khasia Observations 65.8 degrees
Number of Observations 51
1 degree= 369 feet
Altitude above the Sea 5,143 feet

Amwee
Date September 23
Calcutta Observations 79.9 degrees
Number of Observations 15
Khasia Observations 67.1 degrees
Number of Observations 11
1 degree= 396 feet
Altitude above the Sea 4,105 feet

Joowy
Date September 23
Calcutta Observations 79.5 degrees
Number of Observations 11
Khasia Observations 69.0 degrees
Number of Observations 7
1 degree= 567 feet
Altitude above the Sea 4,387 feet

Total Calcutta Observations 400
Total Khasia Observations 434
Mean 1 degree= 385 feet

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.

APPENDIX J.

ON THE MEASUREMENT OF ALTITUDES BY THE BOILING-POINT THERMOMETER.

The use of the boiling-point thermometer for the determination of
elevations in mountainous countries appearing to me to be much
underrated, I have collected the observations which I was enabled to
take, and compared their results with barometrical ones.

I had always three boiling-point thermometers in use, and for several
months five; the instruments were constructed by Newman, Dollond,
Troughton, and Simms, and Jones, and though all in one sense good
instruments, differed much from one another, and from the truth.
Mr. Welsh has had the kindness to compare the three best instruments
with the standards at the Kew Observatory at various temperatures
between 180 degrees and the boiling-point; from which comparison it
appears, that an error of l.5 degrees may be found at some parts of
the scale of instruments most confidently vouched for by admirable
makers. Dollond's thermometer, which Dr. Thomson had used throughout
his extensive west Tibetan journeys, deviated but little from the
truth at all ordinary temperatures. All were so far good, that the
errors, which were almost entirely attributable to carelessness in
the adjustments, were constant, or increased at a constant ratio
throughout all parts of the scale; so that the results of the
different instruments have, after correction, proved strictly
comparable.

The kettle used was a copper one, supplied by Newman, with free
escape for the steam; it answered perfectly for all but very high
elevations indeed, where, from the water boiling at very low
temperatures, the metal of the kettle, and consequently of the
thermometer, often got heated above the temperature of the
boiling water.

I found that no confidence could be placed in observations taken at
great elevations, by plunging the thermometer in open vessels of
boiling water, however large or deep, the abstraction of heat from
the surface being so rapid, that the water, though boiling below, and
hence bubbling above, is not uniformly of the same temperature
throughout.

In the Himalaya I invariably used distilled, or snow or rain-water;
but often as I have tried common river-water for comparison, I never
found that it made any difference in the temperature of the
boiling-point. Even the mineral-spring water at Yeumtong, and the
detritus-charged glacial streams, gave no difference, and I am hence
satisfied that no objection can be urged against river waters of
ordinary purity.

On several occasions I found anomalous rises and falls in the column
of mercury, for which I could not account, except theoretically, by
assuming breaks in the column, which I failed to detect on lifting
the instrument out of the water; at other times, I observed that the
column remained for several minutes stationary, below the true
temperature of the boiling water, and then suddenly rose to it.
These are no doubt instrumental defects, which I only mention as
being sources of error against which the observer must be on the
watch: they can only be guarded against by the use of two
instruments.

With regard to the formula employed for deducing the altitude from a
boiling-point observation, the same corrections are to a great extent
necessary as with barometric observations: if no account is taken of
the probable state of atmospheric pressure at the level of the sea at
or near the place of observation, for the hour of the day and month
of the year, or for the latitude, it is obvious that errors of 600 to
1000 feet may be accumulated. I have elsewhere stated that the
pressure at Calcutta varies nearly one inch (1000 feet), between July
and January; that the daily tide amounts to one-tenth of an inch
(=100 feet); that the multiplier for temperature is too great in the
hot season and too small in the cold; and I have experimentally
proved that more accuracy is to be obtained in measuring heights in
Sikkim, by assuming the observed Calcutta pressure and temperature to
accord with that of the level of the sea in the latitude of Sikkim,
than by employing a theoretical pressure and temperature for the
lower station.

In the following observations, the tables I used were those printed
by Lieutenant-Colonel Boileau for the East India Company's Magnetic
Observatory at Simla, which are based upon Regnault's Table of the
'Elastic Force of Vapour.' The mean height of the barometrical column
is assumed (from Bessel's formula) to be 29.924 at temp. 32 degrees,
in lat. 45 degrees, which, differing only .002 from the barometric
height corresponding to 212 degrees Fahrenheit, as determined
experimentally by Regnault, gives 29.921 as the pressure
corresponding to 212 degrees at the level of the sea.

The approximate height in feet corresponding to each degree of the
boiling-point, is derived from Oltmann's tables. The multipliers for
the mean temperature of the strata of atmosphere passed through, are
computed for every degree Fahrenheit, by the formula for expansion
usually employed, and given in Baily's Astronomical Tables and Biot's
Astronomie Physique.

For practical purposes it may be assumed that the traveller, in
countries where boiling-point observations are most desired, has
never the advantage of a contemporaneous boiling-point observation at
a lower station. The approximate difference in height is hence, in
most cases, deduced from the assumption, that the boiling-point
temperature at the level of the sea, at the place of observation, is
212 degrees, and that the corresponding temperature of the air at the
level of the sea is hotter by one degree for every 330 feet of
difference in elevation. As, however, the temperature of boiling
water at the level of the sea varies at Calcutta between July and
January almost from 210.7 degrees to 212.6 degrees, I always took the
Calcutta barometer observation at the day and hour of my
boiling-point observation, and corrected my approximate height by as
many feet as correspond to the difference between the observed height
of the barometer at Calcutta and 29.921; this correction was almost
invariably (always normally) subtractive in the summer, often
amounting to upwards of 400 feet: it was additive in winter, and
towards the equinoxes it was very trifling.

For practical purposes I found it sufficient to assume the Calcutta
temperature of the air at the day and hour of observation to be that
of the level of the sea at the place of observation, and to take out
the multiplier, from the mean of this and of the temperature at the
upper station. As, however, 330 feet is a near approach to what I
have shown (Appendix I.) to be the mean equivalent of 1 degree for
all elevations between 6000 and 18,000 feet; and as the majority of
my observations were taken between these elevations, it results that
the mean of all the multipliers employed in Sikkim for forty-four
observations amounts to 65.1 degrees Fahrenheit, using the Calcutta
and upper station observations, and 65.3 degrees on the assumption of
a fall of 1 degree for every 330 feet. To show, however, how great an
error may accrue in individual cases from using the formula of
1 degree to 330, I may mention that on one occasion, being at an
elevation of 12,000 feet, with a temperature of the air of 70
degrees, the error amounted to upwards of 220 feet, and as the same
temperature may be recorded at much greater elevations, it follows
that in such cases the formula should not be employed without
modification.

A multitude of smaller errors, arising from anomalies in the
distribution of temperature, will be apparent on consulting my
observations on the temperature at various elevations in Sikkim;
practically these are unavoidable. I have also calculated all my
observations according to Professor J. Forbes's formula of 1 degree
difference of temperature of boiling-water, being the equivalent of
550 feet at all elevations. (See Ed. Phil. Trans., vol xv. p. 405.)
The formula is certainly not applicable to the Sikkim Himalaya; on
the contrary, my observations show that the formula employed for
Boileau's tables gives at all ordinary elevations so very close an
approach to accuracy on the mean of many observations, that no
material improvement in its construction is to be anticipated.

At elevations below 4000 feet, elevations calculated from the
boiling-point are not to be depended on; and Dr. Thomson remarked the
same in north-west India: above 17,000 feet also the observations are
hazardous, except good shelter and a very steady fire is obtainable,
owing to the heating of the metal above that of the water. At all
other elevations a mean error of 100 feet is on the average what is
to be expected in ordinary cases. For the elevation of great mountain
masses, and continuously elevated areas, I conceive that the results
are as good as barometrical ones; for the general purposes of
botanical geography, the boiling-point thermometer supersedes the
barometer in point of practical utility, for under every advantage,
the transport of a glass tube full of mercury, nearly three feet
long, and cased in metal, is a great drawback to the unrestrained
motion of the traveller.

In the Khasia mountains I found, from the mean of twelve stations and
twenty-three observations, the multiplier as derived from the mean of
the temperature at the upper station and at Calcutta, to be 75.2
degrees, and as deduced from the formula to be 73.1 degrees.
Here, however, the equivalent in feet for 1 degree temp. is in summer
very high, being 1 degree=385 feet. (See Appendix I.) The mean of all
the elevations worked by the boiling-point is upwards of 140 feet
below those worked by the barometer.

The following observations are selected as having at the time been
considered trustworthy, owing to the care with which they were taken,
their repetition in several cases, and the presumed accuracy of the
barometrical or trigonometrical elevation with which they are
compared. A small correction for the humidity of the air might have
been introduced with advantage, but as in most barometrical
observations, the calculations proceed on the assumption that the
column of air is in a mean state of saturation; as the climate of the
upper station was always very moist, and as most of the observations
were taken during the rains, this correction would be always
additive, and would never exceed sixty feet.

It must be borne in mind that the comparative results given below
afford by no means a fair idea of the accuracy to be obtained by the
boiling-point. Some of the differences in elevation are probably due
to the barometer. In other cases I may have read off the scale wrong,
for however simple it seems to read off an instrument, those
practically acquainted with their use know well how some errors
almost become chronic, how with a certain familiar instrument the
chance of error is very great at one particular part of the scale,
and how confusing it is to read off through steam alternately from
several instruments whose scales are of different dimensions, are
differently divided, and differently lettered; such causes of error
are constitutional in individual observers. Again, these observations
are selected without any reference to other considerations but what I
have stated above; the worst have been put in with the best. Had I
been dependent on the boiling-point for determining my elevations, I
should have observed it oftener, or at stated periods whenever in
camp, worked the greater elevations from the intermediate ones, as
well as from Calcutta, and resorted to every system of interpolation.
Even the following observations would be amended considerably were I
to have deduced the elevation by observations of the boiling-point at
my camp, and added the height of my camp, either from the
boiling-point observations there, or by barometer, but I thought it
better to select the most independent method of observation, and to
make the level of the sea at Calcutta the only datum for a lower
station.

SERIES I.--_Sikkim Observations._

Elev. by
Barom. or Temp. Elev.
Place. Month. Trigonom. B.P. Air by B.P. Error
(feet) (feet) (feet)
------------------------------------------------------------------------
Great Rungeet river Feb. B 818 210.7 56.3 904 + 86
Bhomsong Dec. 1,544 210.2 58.0 1,321 -223
Guard House, Gt Rungeet April 1,864 208.1 72.7 2,049 +185
Choongtam Aug. 5,268 202.6 65.0 5,175 - 93
Dengha Aug. 6,368 200.6 68.0 6,246 -122
Mr. Muller's (Dorjiling) Feb. Tr 6,925 199.4 41.3 7,122 +197
Dr. Campbell's (do.) April 6,932 200.1 59.5 6,745 -187
Mr. Hodgson's (do.) Feb. B 7,429 199.4 47.6 7,318 -111
Sinchul Jan. Tr 8,607 197.0 41.7 8,529 - 78
Lachoong Aug. B 8,712 196.4 54.6 8,777 + 65
Lamteng Aug. 8,884 196.3 77.0 8,937 + 53
Zemu Samdong July 8,976 196.1 58.6 8,916 - 60
Mainom Dec. Tr 10,702 193.4 38.0 10,516 -186
Junct. of Zemu & Thlonok July B 10,846 193.6 52.0 10,872 + 26
Tallum July 11,482 191.8 54.6 11,451 - 31
Yeumtong Sept. 11,919 191.3 52.2 11,887 - 32
Zemu river June 12,070 190.4 48.5 12,139 + 69
Tungu July & 12,751 189.7 43.4 12,696 - 55
Oct.
Jongri Jan. 13,194 188.8 26.0 13,151 - 43
Zemu river June 13,281 188.5 47.0 13,360 + 79
Lachee-pia Aug. 15,262 186.0 42.8 14,912 -350
Momay Sept. 15,362 186.1 48.6 14,960 -402
Palung Oct. 15,620 185.4 45.8 15,437 -183
Kongra Lama July 15,694 184.1 41.5 16,041 +347
Snow-bed above Yeumtong Sept. 15,985 184.6 44.5 15,816 -169
Tunkra pass Aug. 16,083 164.1 39.0 16,137 + 54
Yeumtso Oct. 16,808 183.1 15.0 16,279 -529
Donkia Sept. 16,978 182.4 41.0 17,049 + 71
Mountain above Momay Sept. 17,394 181.9 47.8 17,470 + 76
Sebolah pass Sept. 17,585 181.9 46.5 17,517 - 68
Kinchinjhow Sept. 17,624 181.0 47.5 18,026 +402
Donkia Mountain Sept. 18,510 180.6 37.1 18,143 -367
Ditto Sept. 18,307 179.9 38.8 18,597 +290
Bhomtso Oct. 18,450 181.2 52.0 18,305 -145
Donkia pass Sept. 18,466 181.2 45.5 17,866 -600
------------------------------------------------------------------------
Mean - 58