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
SERIES II.—Khasia Mountains.
Elev. Elev.
Place Month Bar. B.P. Tm. Air by B.P. Diff.
(feet) (feet) (feet)
———————————————————————————————————
Churra June 4,069 204.4 70.3 4,036 - 33
Amwee Sept. 4,105 205.1 67.7 4,041 - 64
Nurtiung Oct. 4,178 205.0 70.0 4,071 -107
Nunklow July 4,688 203.9 69.8 4,333 -355
Kala-panee June, July, 5,302 202.2 65.8 5,202 -100
Sept., Oct.
Myrung July 5,647 201.9 69.4 5,559 - 88
Syong July 5,725 201.8 70.8 5,632 - 93
Moflong July, Aug., 6,062 201.4 64.8 5,973 - 89
Oct., Nov.
Chillong Nov. 6,662 201.2 62.8 6,308 -354
———————————————————————————————————
Mean 5,160 5,016 -143
APPENDIX K.
ACTTNOMETER OBSERVATIONS.
The few actinometer observations which I was enabled to record, were made with two of these instruments constructed by Barrow, and had the bulbs of their thermometers plunged into the fluid of the chamber. They were taken with the greatest care, in conformity with all the rules laid down in the "Admiralty Guide," and may, I think, be depended upon. In the Sikkim Himalaya, a cloudless day, and one admitting of more than a few hours' consecutive observations, never occurs—a day fit for any observation at all is very, rare indeed. I may mention here that a small stock of ammonia-sulphate of copper in crystals should be supplied with this instrument, also a wire and brush for cleaning, and a bottle with liquid ammonia: all of which might be packed in the box.
Active 6.568. Time always mean.
Jillapahar, Dorjiling, Elev. 7430 feet, Lat. 27 degrees 3 minutes N., Long. 88 degrees 13 minutes E.
A.— APRIL 19th, 1850. Watch slow 1 minute 15 seconds mean time.
Tem. Act.
Hour Act. Act. Reduced Barom. Air
—————————————————————————————————
a.m. 8.0 to 8.13 11.1 65.5 0.9900 22.960 53.5
8.15 to 8.28 15.0 69.5 12.2645
9.0 to 9.13 17.7 71.5 14.5140 22.948 56.0
10.0 to 10.13 19.1 72.5 15.4710 22.947 57.0
11.0 to 11.13 19.0 75.0 14.9150 22.946 58.5
p.m. 0.0 to 0.13 18.8 75.0 12.7600 22.944 60.3
1.0 to 1.13 17.2 73.3 13.8976 22.939 59.4
2.0 to 2.13 17.4 74.0 13.8330 22.914 60.3
—————————————————————————————————
Black
Hour D.P. Diff. Sat. Bulb
—————————————————————————————————
a.m. 8.0 to 8.13 33.8 19.7 .505 88.0 Day unexceptional,
8.15 to 8.28 111.5 wind S.W., after
9.0 to 9.13 37.2 18.8 .153 110.0 10 a.m. squally.
10.0 to 10.13 39.7 17.3 .550 121.0
11.0 to 11.13 38.2 20.3 .500 125.0
p.m. 0.0 to 0.13 44.8 15.5 .592 120.0
1.0 to 1.13 40.7 18.7 .546 122.0 Dense haze over
2.0 to 2.13 44.1 16.2 .577 108.0 snowy Mts.
—————————————————————————————————
B.—APRIL 20th Tem. Act. Hour Act. Act. Reduced Barom. Air ————————————————————————————————— a.m. 8.0 to 8.13 11.8 64.0 10.9150 22.969 43.4 9.0 to 9.13 17.8 73.3 14.2750 22.974 36.2 10.0 to 10.13 18.8 65.0 14.7580 22.985 57.0 ————————————————————————————————— Black Hour D.P. Diff. Sat. Bulb ————————————————————————————————— a.m. 8.0 to 8.13 43.4 10.8 .691 74.0 Dense haze, 9.0 to 9.13 44.1 12.1 .662 92.0 S.E. wind, 10.0 to 10.13 42.5 14.5 .609 92.0 cloudless sky. —————————————————————————————————
Superintendent's House, Dorjiling. Elev. 6932 feet. C.—APRIL 21st. Watch slow 1 minute mean time. Tem. Act. Hour Act. Act. Reduced Barom. Air ————————————————————————————————— a.m. 8.35 to 8.48 17.3 65.0 15.7084 56.4 9.07 to 9.20 20.9 72.7 16.8872 23.447 63.8 10.0 to 10.13 23.9 77.3 18.3791 60.8 11.0 to 11.13 24.4 81.0 17.8864 ————————————————————————————————— Black Hour D.P. Diff. Sat. Bulb ————————————————————————————————— a.m. 8.35 to 8.48 47.6 8.8 .741 97.0 Day very fine, 9.07 to 9.20 49.9 13.9 .628 100.0 snowy Mts. in 10.0 to 10.13 49.2 11.6 .677 109.0 dull red haze, 11.0 to 11.13 107.5 wind S.E. faint. —————————————————————————————————
Rampore Bauleah (Ganges). Elev. 130 feet. Lat. 22 degrees 24 minutes N., Long. 88 degrees 40 minutes E.
MAY 17th, 1850.
Watch slow 15 seconds mean time.
Tem. Act.
Hour Act. Act. Reduced Barom. Air
—————————————————————————————————
a.m. 7.51 to 8.13 13.0 88.0 8.8790 29.698 87.5
9.03 to 9.16 19.5 96.0 12.5190 92.0
9.20 to 9.33 21.2 107.0 12.7836 29.615 92.3
11.15 to 11.28 21.1 105.0 12.8499 98.5
11.32 to 11.45 16.5 108.7 9.8770 29.620 98.3
p.m. 1.20 to 1.33 21.6 108.5 12.9348 104.5
1.40 to 1.53 21.4 113.7 12.4976 105.8
—————————————————————————————————
Black
Hour D.P. Diff. Sat. Bulb
—————————————————————————————————
a.m. 7.51 to 8.13 80.1 7.4 .793 91.0 S.E. wind, very
9.03 to 9.16 81.2 10.8 .715 83.8 hazy to west, sky
9.20 to 9.33 80.2 12.1 .687 132.0 pale blue.
11.15 to 11.28 74.8 23.7 .478 98.5 Wind west, rising.
11.32 to 11.45 74.3 24.0 .475 142.0
p.m. 1.20 to 1.33 76.7 27.8 .425 144.0
1.40 to 1.53 72.2 33.6 .355 134.0
—————————————————————————————————
Churra, Khasia Mountains. Elev. 4225 feet, Lat. 25 degrees 15 minutes N., Long. 91 degrees 47 minutes E. A—NOVEMBER 4th, 1850. Watch slow 7 minutes mean time. Tem. Act. Hour Act. Act. Reduced Barom. Air ————————————————————————————————— a.m. 6.20 to 6.30 5.0 63.7 4.6400 25.781 57.8 6.32 to 6.42 7.4 65.4 6.6896 59.0 7.55 to 8.05 20.0 77.5 15.2400 63.5 8.08 to 8.18 21.0 82.0 15.2040 64.4 8.20 to 8.30 24.2 85.8 10.8432 64.8 ————————————————————————————————— Black Hour D.P. Diff. Sat. Bulb ————————————————————————————————— a.m. 6.20 to 6.30 53.1 4.7 .850 75.0 Sky faint blue, 6.32 to 6.42 54.8 4.2 .870 83.0 cloudless, 7.55 to 8.05 56.9 6.6 .806 108.0 wind S.W., 8.08 to 8.18 57.3 7.1 .790 106.5 clouding. 8.20 to 8.30 59.5 5.3 .837 113.5 —————————————————————————————————
B.—NOVEMBER 5th.
Watch slow 7 minutes mean time.
Tem. Act.
Hour Act. Act. Reduced Air
——————————————————————————-
a.m. 6.39 to 6.49 11.2 70.2 9.3408 59.4
6.51 to 7.01 13.4 72.8 10.8138 60.5
7.56 to 8.06 18.4 73.2 15.0161 61.7
8.08 to 8.21 20.4 77.7 15.4836 63.3
9.26 to 9.36 23.8 79.5 17.8072
9.37 to 9.47 25.1 84.0 17.7959
10.57 to 11.07 29.0 89.5 19.5460 66.7
——————————————————————————-
Black
Hour D.P. Diff. Sat. Bulb
—————————————————————————————————
a.m. 6.39 to 6.49 57.6 1.8 .940 Wind S.W.,
6.51 to 7.01 57.8 2.7 .918 clouds rise and
7.56 to 8.06 57.7 4.0 .875 disperse.
8.08 to 8.21 58.7 4.6 .860 Sky pale.
9.26 to 9.36
9.37 to 9.47
10.57 to 11.07 60.8 5.9 8.28 126.0
—————————————————————————————————
C.—NOVEMBER 6th.
Watch slow 7 minutes mean time.
Tem. Act.
Hour Act. Act. Reduced Barom. Air
—————————————————————————————————
a.m. 6.05 to 6.18 2.6 62.0 2.4986 25.781 56.5
6.22 to 6.35 6.5 63.5 6.0710 57.0
6.38 to 6.51 9.6 66.7 8.5152 61.0
8.27 to 8.37 21.7 78.8 16.2750 64.2
8.39 to 8.52 23.0 81.7 19.4750 64.5
—————————————————————————————————
Black
Hour D.P. Diff. Sat. Bulb
—————————————————————————————————
a.m. 6.05 to 6.18 54.5 2.0 .935 Sunrise, 6, pale
6.22 to 6.35 55.1 1.9 .935 yellow red,
6.38 to 6.51 57.4 3.6 .888 cloudless.
8.27 to 8.37 59.3 4.9 .855 100.0 Cirrhus below.
8.39 to 8.52 59.4 5.1 .847 105.0
—————————————————————————————————
D.—NOVEMBER 14th.
Tem. Act.
Hour Act. Act. Reduced Barom. Air
—————————————————————————————————
a.m. 6.12 to 6.22 2.9 60.6 3.5988 25.783 51.5
6.24 to 6.37 6.1 66.0 5.4472 52.7
7.13 to 7.23 12.4 70.8 10.2672 56.5
7.24 to 7.34 14.7 76.0 11.4025 57.8
8.34 to 8.44 19.9 82.8 14.2653 59.8
8.47 to 9.00 21.7 88.8 14.7343 60.5
9.53 to 10.03 23.5 86.6 16.2620 25.832 67.2
10.04 to 10.17 25.3 89.5 17.0775 67.0
11.24 to 11.31 33.3 111.5 20.7014 25.819 64.6
—————————————————————————————————
Black
Hour D.P. Diff. Sat. Bulb
—————————————————————————————————
a.m. 6.12 to 6.22 49.4 2.1 .930
6.24 to 6.37 50.3 2.4 .925
7.13 to 7.23 52.3 4.2 .900 98.0 Thick cumulus low
7.24 to 7.34 53.1 4.7 .855 104.0 on plains.
8.34 to 8.44 50.8 9.0 .742 117.0 Sunrise yellow
8.47 to 9.00 51.6 8.9 .730 121.0 red.
9.53 to 10.03 61.6 5.6 .832 127.0 Cloudless.
10.04 to 10.17 58.8 8.2 .778 133.0
11.24 to 11.31 59.0 5.6 .832 130.0 Clouds rise.
—————————————————————————————————
E.—NOVEMBER 15th.
Tem. Act.
Hour Act. Act. Reduced Barom. Air
—————————————————————————————————
a.m. 9.53 to 10.06 25.8 78.0 17.5306 25.854 63.0
10.50 to 11.03 26.1 80.5 19.1835 64.0
11.31 to 11.44 28.5 84.0 20.2065 65.3
p.m. 0.33 to 0.46 30.9 91.5 20.4267 25.844 65.8
1.07 to 1.21 29.1 90.5 20.4388 67.0
2.47 to 3.00 21.1 75.0 16.5653 25.808 67.2
3.48 to 4.00 16.7 73.0 13.4435 62.0
4.03 to 4.16 16.2 75.0 12.7170 25.803 61.5
—————————————————————————————————
Hour D.P. Diff. Sat.
——————————————————————————————-
a.m. 9.53 to 10.06 55.3 8.7 .772 Sky cloudless.
10.50 to 11.03 52.8 11.2 .690 Wind N.E.
11.31 to 11.44 51.9 13.4 .638
p.m. 0.33 to 0.46 51.2 14.6 .620
1.07 to 1.21 49.6 17.4 .560
2.47 to 3.00 56.6 10.6 .708
3.48 to 4.00 50.8 11.2 .690
4.03 to 4.16 50.5 11.0 .692
——————————————————————————————-
Silchar (Cachar), Elev. 116 feet, Lat. 24 degrees 30 minutes N., Long. 93 degrees E. (approximate).
NOVEMBER 26th, 1850 Watch slow 13 minutes 39 seconds mean time.
Tem. Act.
Hour Act. Act. Reduced Barom. Air
—————————————————————————————————
a.m. 9.11 to 9.24 19.4 69.0 16.4706 66.3
9.34 to 9.41 22.7 81.0 16.5937
9.50 to 9.57 25.3 87.5 17.3558 29.999 68.7
10.07 to 10.14 26.5 91.5 17.5695 70.3
11.03 to 11.16 26.3 89.0 17.5251 73.2
p.m. 0.00 to 0.13 26.4 90.0 17.8144 29.967 74.5
0.58 to 1.11 27.6 94.0 17.9676 76.8
2.51 to 3.04 23.0 93.0 15.0880 29.892 78.5
3.55 to 4.08 17.6 91.5 11.6688 79.5
4.09 to 4.22 15.5 93.5 11.0215 29.881 79.4
4.23 to 4.36 12.0 93.7 7.8360 78.5
—————————————————————————————————
Hour D.P. Diff. Sat.
——————————————————————————————-
a.m. 9.11 to 9.24 63.5 2.8 .860 Dense fog till
9.34 to 9.41 7.30 p.m.
9.50 to 9.57 61.5 7.2 .788 Wind north. Clear.
10.07 to 10.14 62.7 7.6 .780
11.03 to 11.16 60.3 12.9 .657 Wind. N.E. Light
p.m. 0.00 to 0.13 61.7 12.8 .658 cirrhus low.
0.58 to 1.11 60.3 16.5 .586
2.51 to 3.04 62.1 16.4 .588 Streaks of cirrhus
3.55 to 4.08 57.0 22.5 .480 aloft.
4.09 to 4.22 62.1 17.3 .570
4.23 to 4.36 62.1 16.4 .588 Sun sets in hazy
cirrhus.
——————————————————————————————-
Chittagong, Elev. 200 feet, Lat. 22 degrees 20 minutes N., Long. 91 degrees 55 minutes E.
A.—DECEMBER 31st, 1850.
Watch slow 3 minutes 45 seconds mean time.
Tem. Act.
Hour Act. Act. Reduced Barom. Air
—————————————————————————————————
a.m. 7.39 to 7.52 10.0 70.0 8.3700 57.0
8.40 to 8.53 21.3 91.5 14.1219 29.874 59.5
9.04 to 9.08 23.2 89.5 15.6163 63.3
9.52 to 9.56 24.3 87.3 16.7341 29.923 64.5
10.02 to 10.06 25.1 90.5 16.7668 65.7
11.16 to 11.29 24.3 84.5 17.1558 68.5
11.52 to 11.56 26.6 92.6 17.5028 29.892 69.5
p.m. 1.38 to 1.41 24.7 84.0 17.5123 71.7
1.47 to 1.51 25.4 90.7 16.8418
3.10 to 3.17 21.1 86.0 14.6645 29.831 71.0
3.18 to 3.25 19.3 89.3 13.0468
—————————————————————————————————
Black
Hour D.P. Diff. Sat. Bulb
—————————————————————————————————
a.m. 7.39 to 7.52 55.7 1.3 .960 Cloudless.
8.40 to 8.53 57.2 2.3 .920 127.0 Mountains clear.
9.04 to 9.08 59.7 3.6 .890 Wind E.N.E. Cool.
9.52 to 9.56 61.3 3.2 .900 142.0
10.02 to 10.06 60.4 5.3 .840 148.0 Wind N.W.
11.16 to 11.29 58.6 9.9 .722 150.0
11.52 to 11.56 59.2 10.3 .710 Wind S.W.
p.m. 1.38 to 1.41 61.8 9.9 .720
1.47 to 1.51
3.10 to 3.17 60.5 10.5 .710 Clouds about in
3.18 to 3.25 patches.
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B.— JANUARY 1, 1851.
Watch slow 3 minutes 45 seconds mean time.
Tem. Act.
Hour Act. Act. Reduced Barom. Air
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a.m. 7.34 to 7.41 10.0 69.4 8.4200 29.948 55.4
8.38 to 8.45 16.0 70.0 13.3920 58.9
9.44 to 9.51 19.5 74.7 15.3660 29.891 63.2
10.46 to 10.53 21.0 78.2 15.8550 66.7
11.50 to 11.57 21.5 81.2 15.6950 69.8
p.m. 0.06 to 0.13 24.1 88.0 16.4603 29.850 70.3
0.58 to 1.02 23.9 87.2 16.4432 71.0
1.45 to 1.52 21.4 84.5 15.0870 71.3
3.15 to 3.22 18.1 82.5 13.0320 29.798 71.3
4.27 to 4.34 10.2 82.0 7.3746 70.0
4.36 to 4.43 9.8 84.0 6.9482
4.45 to 4.52 8.5 85.0 5.9670
4.56 to 5.09 5.6 85.0 3.9312 67.5
5.12 to 5.18 3.8 84.0 2.6942 29.778 68.7
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Black
Hour D.P. Diff. Sat. Bulb
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a.m. 7.34 to 7.41 54.0 1.4 .953 Mist rises and
8.38 to 8.45 57.7 1.2 .970 104.5 drifts westward
9.44 to 9.51 61.7 1.5 .960 115.0 till 7.30 a.m.
10.46 to 10.53 62.4 4.3 .870 129.0
11.50 to 11.57 58.3 11.5 .688 117.0 Wind N.W., clouds
p.m. 0.06 to 0.13 56.0 14.3 .625 122.5 rise.
0.58 to 1.02 56.7 14.3 .625
1.45 to 1.52 57.5 13.8 .633 117.0
3.15 to 3.22 57.1 14.2 .625
4.27 to 4.34 59.5 10.5 .708
4.36 to 4.43
4.45 to 4.52
4.56 to 5.09 62.7 4.8 .855 Sunset cloudless.
5.12 to 5.18 62.2 6.5 .810
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C.—JANUARY 2, 1851. Watch slow 3 minutes mean time. Tem. Act. Hour Act. Act. Reduced Barom. Air ————————————————————————————————— a.m. 10.02 to 10.09 19.2 71.0 15.8592 64.5 10.20 to 10.24 22.6 79.0 16.9048 29.861 65.6 p.m. 0.03 to 0.10 24.7 89.2 16.6972 29.858 69.0 0.22 to 0.25 25.9 95.5 18.6796 70.7 2.04 to 2.08 23.3 91.5 15.4479 71.2 2.10 to 2.14 23.8 93.0 15.6128 —————————————————————————————————
Black
Hour D.P. Diff. Sat. Bulb
—————————————————————————————————
a.m. 10.02 to 10.09 60.6 3.9 .878 116.0 Low, dense fog at
10.20 to 10.24 61.4 4.2 .872 sunrise, clear at
p.m. 0.03 to 0.10 59.3 9.7 .728 119.0 9 a.m.
0.22 to 0.25 57.5 3.2 .650 Hills hazy and
2.04 to 2.08 61.0 10.2 .718 112.0 horizon grey.
2.10 to 2.14
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