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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° and the boiling-point; from which comparison it appears, that an error of l·5° 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;


 

[ 454 ]

 

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


 

[ 455 ]

 

be 29·924 at temp. 32°, in lat. 45°, which, differing only ·002 from the barometric height corresponding to 212° Fahrenheit, as determined experimentally by Regnault, gives 29·921 as the pressure corresponding to 212° 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°, 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° to 212·6°, 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° 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


 

[ 456 ]

 

observations amounts to 65·1° Fahrenheit, using the Calcutta and upper station observations, and 65·3° on the assumption of a fall of 1° for every 330 feet. To show, however, how great an error may accrue in individual cases from using the formula of 1° 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°, 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° 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


 

[ 457 ]

 

mean of the temperature at the upper station and at Calcutta, to be 75.2°, and as deduced from the formula to be 73·1°. Here, however, the equivalent in feet for 1° temp. is in summer very high, being 1°=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


 

[ 458 ]

 

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.

 

Place Month Elevation
by Barom.
or
Trigonom.
Temp.
B.P.
Air Elevation
by B.P.
Error
 
Great Rungeet river
Bhomsong
Guard House, Great Rungeet
Choongtam
Dengha
Mr. Muller’s (Dorjiling)
Dr. Campbell’s (Dorjiling)
Mr. Hodgson’s (Dorjiling)
Sinchul
Lachoong
Lamteng
Zemu Samdong
Mainom
Junction of Zemu & Thlonok
Tallum
Yeumtong
Zemu river
Tungu
Jongri
Zemu river
Lachee-pia
Momay
Palung
Kongra Lama
Snow-bed above Yeumtong
Tunkra pass
Yeumtso
Donkia
Mountain above Momay
Sebolah pass
Kinchinjow
Donkia Mountain
Donkia Mountain
Bhomtso
Donkia pass
 
Feb.
Dec.
Apr.
Aug.
Aug.
Feb.
Apr.
Feb.
Jan.
Aug.
Aug.
July
Dec.
July
July
Sept.
June
July/Oct.
Jan.
June
Aug.
Sept.
Oct.
July
Sept.
Aug.
Oct.
Sept.
Sept.
Sept.
Sept.
Sept.
Sept.
Oct.
Sept.
(feet)
B.       818
1,544
1,864
5,268
6,368
Tr.   6,925
6,932
B.    7,429
Tr.   8,607
B.    8,712
8,884
8,976
Tr. 10,702
B.  10,846
11,482
11,919
12,070
12,751
13,194
13,281
15,262
15,362
15,620
15,694
15,985
16,083
16,808
16,978
17,394
17,585
17,624
18,510
18,307
18,450
18,466
 
210·7
210·2
208·1
202·6
200·6
199·4
200·1
199·4
197·0
196·4
196·3
196·1
193·4
193·6
191·8
191·3
190·4
189·7
188·8
188·5
186·0
186·1
185·4
184·1
184·6
164·1
183·1
182·4
181·9
181·9
181·0
180·6
179·9
181·2
181·2
 
56·3
58·0
72·7
65·0
68·0
41·3
59·5
47·6
41·7
54·6
77·0
58·6
38·0
52·0
54·6
52·2
48·5
43·4
26·0
47·0
42·8
48·6
45·8
41·5
44·5
39·0
15·0
41·0
47·8
46·5
47·5
37·1
38·8
52·0
45·5
(feet)
    904
  1,321
  2,049
  5,175
  6,246
  7,122
  6,745
  7,318
  8,529
  8,777
  8,937
  8,916
10,516
10,872
11,451
11,887
12,139
12,696
13,151
13,360
14,912
14,960
15,437
16,041
15,816
16,317
16,279
17,049
17,470
17,517
18,026
18,143
18,597
18,305
17,866
(feet)
+   86
– 223
+ 185
–   93
– 122
+ 197
– 187
– 111
–   78
+   65
+   53
–   60
– 186
+   26
–   31
–   32
+   69
–   55
–   43
+   79
– 350
– 402
– 183
+ 347
– 169
+   54
– 529
+   71
+   76
–   68
+ 402
– 367
+ 290
– 145
– 600
  Mean         –   58



 

[ 459 ]

 

SERIES II.—Khasia Observations.

 

Place Month Elevation
by
Barometer
Temp.
B.P.
Air Elevation
by B.P.
Diff.
 
Churra
Amwee
Nurtiung
Nunklow
Kala-panee
 
Myrung
Syong
Moflong
 
Chillong
 
June
September
October
July
June, July,
Sept., Oct.
July
July
July, Aug.,
Oct., Nov.
November
(feet)
4,069
4,105
4,178
4,688
5,302
 
5,647
5,725
6,062
 
6,662
 
204·4
205·1
205·0
203·9
202·2
 
201·9
201·8
201·4
 
201·2
 
70·3
67·7
70·0
69·8
65·8
 
69·4
70·8
64·8
 
62·8
(feet)
4,036
4,041
4,071
4,333
5,202
 
5,559
5,632
5,973
 
6,308
(feet)
–   33
–   64
– 107
– 355
– 100
 
–   88
–   93
–   89
 
– 354
  Mean 5,160     5·016 – 143


 


 
K.

ACTINOMETER 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.


 

[ 460 ]

 


 

Jillapahar, Dorjiling, Elev. 7,430 feet, Lat. 27° 3′ N., Long. 88° 13′ E.

 

A.—APRIL 19TH, 1850.   Watch slow 1′ 15″ mean time.

 

Hour Act. Temp.
Act.
Act.
reduced
Barom. Air D.P. Diff. Sat. Black
Bulb
 
8.00 to 8.13 a.m.
8.15 to 8.28 a.m.
9.00 to 9.13 a.m.
10.00 to 10.13 a.m.
11.00 to 11.13 a.m.
Noon to 12.13 p.m.
1.00 to 1.13 p.m.
2.00 to 2.13 p.m.
11·1
15·0
17·7
19·1
19·0
18·8
17·2
17·4
65·5
69·5
71·5
72·5
75·0
75·0
73·3
74·0
  9·9900
12·2645
14·5140
15·4710
14·9150
12·7600
13·8976
13·8330
22·960
 
22·948
22·947
22·946
22·944
22·939
22·914
53·5
 
56·0
57·0
58·5
60·3
59·4
60·3
33·8
 
37·2
39·7
38·2
44·8
40·7
44·1
19·7
 
18·8
17·3
20·3
15·5
18·7
16·2
·505
 
·513
·550
·500
·592
·546
·577
  88·0
111·5
110·0
121·0
125·0
120·0
122·0
108·0
Day unexceptional,
wind S.W.,
after 10 a.m. squally.
 
 
 
Dense haze over
snowy mountains.


 

B.—APRIL 20TH.

 

Hour Act. Temp.
Act.
Act.
reduced
Barom. Air D.P. Diff. Sat. Black
Bulb
 
8.0 to 8.30 a.m.
9.0 to 9.13 a.m.
10.0 to 10.13 a.m.
11·8
17·8
18·8
64·0
73·3
65·0
10·9150
14·2750
14·7580
22·969
22·974
22·985
54·2
56·2
57·0
43·4
44·1
42·5
10·8
12·1
14·5
·691
·662
·609
74·0
92·0
92·0
Dense haze,
S.E. wind,
cloudless sky.


 


 

Superintendent's House, Dorjiling, Elev. 6,932 feet.

 

C.—APRIL 21ST.   Watch slow 1′ mean time.

 

Hour Act. Temp.
Act.
Act.
reduced
Barom. Air D.P. Diff. Sat. Black
Bulb
 
8.35 to 8.48 a.m.
9.07 to 9.20 a.m.
10.00 to 10.13 a.m.
11.00 to 11.13 a.m.
17·3
20·9
23·9
24·4
65·0
72·7
77·3
81·0
15·7084
16·8872
18·3791
17·8864
 
23·447
56·4
63·8
60·8
47·6
49·9
49·2
  8·8
13·9
11·6
·741
·628
·677
  97.0
100·0
109·0
107·5
Day very fine,
snowy mts. in
dull red haze,
wind S.E. faint.


 


 

Rampore Bauleah (Ganges). Elev. 130 feet, Lat. 24° 24′ N., Long. 88° 40′ E.

 

MAY 17TH, 1850.   Watch slow 15″ mean time.

 

Hour Act. Temp.
Act.
Act.
reduced
Barom. Air D.P. Diff. Sat. Black
Bulb
 
7.51 to 8.13 a.m.
9.03 to 9.17 a.m.
9.20 to 9.33 a.m.
11.15 to 11.28 a.m.
11.32 to 11.45 a.m.
1.20 to 1.33 p.m.
1.40 to 1.53 p.m.
13·0
19·5
21·2
21·1
16·5
21·6
21·4
  88·0
  96·0
107·0
105·0
108·7
108·5
113·7
  8·8790
12·5190
12·7836
12·8499
  9·8770
12·9348
12·4976
29·698
 
29·615
 
29·620
87·5
92·0
92·3
98·5
98·3
104·5  
105·8  
80·1
81·2
80·2
74·8
74·3
76·7
72·2
  7·4
10·8
12·1
23·7
24·0
27·8
33·6
·793
·715
·687
·478
·475
·425
·355
  91·0
  83·8
132·0
  98·5
142·0
144·0
134·0
S.E. wind, very
hazy to west,
sky pale blue.
Wind west,
rising.



 

[ 461 ]

 


 

Churra, Khasia Mountains. Elev. 4,225 feet, Lat. 25° 15′ N., Long. 91° 47′ E.

 

A.—NOVEMBER 4TH, 1850.   Watch slow 7′ mean time.

 

Hour Act. Temp.
Act.
Act.
reduced
Barom. Air D.P. Diff. Sat. Black
Bulb
 
6.20 to 6.30 a.m.
6.32 to 6.42 a.m.
7.55 to 8.05 a.m.
8.08 to 8.18 a.m.
8.20 to 8.30 a.m.
  5·0
  7·4
20·0
21·0
24·2
63·7
65·4
77·5
82·0
85·8
  4·6400
  6·6896
15·2400
15·2040
16·8432
25·781 57·8
59·0
63·5
64·4
64·8
53·1
54·8
56·9
57·3
59·5
4·7
4·2
6·6
7·1
5·3
·850
·870
·806
·790
·837
  75·0
  83·0
108·0
106·5
113·5
Sky faint blue,
cloudless, wind
S.W., clouding.


 

B.—NOVEMBER 5TH.   Watch slow 7′ mean time.

 

Hour Act. Temp.
Act.
Act.
reduced
Air D.P. Diff. Sat. Black
Bulb
 
6.39 to 6.49 a.m.
6.51 to 7.01 a.m.
7.56 to 8.06 a.m.
8.08 to 8.21 a.m.
9.26 to 9.36 a.m.
9.37 to 9.47 a.m.
10.57 to 11.07 a.m.
11·2
13·4
18·4
20·4
23·8
25·1
29·0
70·2
72·8
73·2
77·7
79·5
84·0
89·5
  9·3408
10·8138
15·0161
15·4836
17·8072
17·7959
19·5460
59·4
60·5
61·7
63·3
 
 
66·7
57·6
57·8
57·7
58·7
 
 
60·8
1·8
2·7
4·0
4·6
 
 
5·9
·940
·918
·875
·860
 
 
8·28
126·0 Wind S.W.,
clouds rise and
disperse. Sky pale.


 

C.—NOVEMBER 6TH.   Watch slow 7′ mean time.

 

Hour Act. Temp.
Act.
Act.
reduced
Barom. Air D.P. Diff. Sat. Black
Bulb
 
6.05 to 6.18 a.m.
6.22 to 6.35 a.m.
6.38 to 6.51 a.m.
8.27 to 8.37 a.m.
8.39 to 8.52 a.m.
2·6
6·5
9·6
21·7  
23·0  
62·0
63·5
66·7
78·8
81·7
2·4986
6·0710
8·5152
16·2750  
19·4750  
25·781 56·5
57·0
61·0
64·2
64·5
54·5
55·1
57·4
59·3
59·4
2·0
1·9
3·6
4·9
5·1
·935
·935
·888
·855
·847
 
 
 
100·0
105·0
Sunrise, 6, pale
yellow red,
cloudless.
Cirrhus below.


 

D.—NOVEMBER 14TH, 1850.

 

Hour Act. Temp.
Act.
Act.
reduced
Barom. Air D.P. Diff. Sat. Black
Bulb
 
6.12 to 6.22 a.m.
6.24 to 6.37 a.m.
7.13 to 7.23 a.m.
7.24 to 7.34 a.m.
8.34 to 8.44 a.m.
8.47 to 9.00 a.m.
9.53 to 10.03 a.m.
10.04 to 10.17 a.m.
11.24 to 11.31 a.m.
  2·9
  6·1
12·4
14·7
19·9
21·7
23·5
25·3
33·3
60·6
66·0
70·8
76·0
82·8
88·8
86·6
89·5
111·5  
  3·5988
  5·4472
10·2672
11·4025
14·2653
14·7343
16·2620
17·0775
20·7014
25·783
 
 
 
 
 
25·832
 
25·819
51·5
52·7
56·5
57·8
59·8
60·5
67·2
67·0
64·6
49·4
50·3
52·3
53·1
50·8
51·6
61·6
58·8
59·0
2·1
2·4
4·2
4·7
9·0
8·9
5·6
8·2
5·6
·930
·925
·900
·855
·742
·730
·832
·778
·832
 
 
  98·0
104·0
117·0
121·0
127·0
133·0
130·0
 
 
Thick cumulus
low on plains.
Sunrise yellow
red.
Cloudless.
 
Clouds rise.

 

[ 462 ]

 

E.—NOVEMBER 15TH, 1850.

 

Hour Act. Temp.
Act.
Act.
reduced
Barom. Air D.P. Diff. Sat.  
9.53 to 10.06 a.m.
10.50 to 11.03 a.m.
11.31 to 11.44 a.m.
12.33 to 12.46 p.m.
1.07 to 1.21 p.m.
2.47 to 3.00 p.m.
3.48 to 4.00 p.m.
4.03 to 4.16 p.m.
25·8
26·1
28·5
30·9
29·1
21·1
16·7
16·2
78·0
80·5
84·0
91·5
90·5
75·0
73·0
75·0
17·5306
19·1835
20·2065
20·4267
20·4388
16·5635
13·4435
12·7170
25·854
 
 
25·844
 
25·808
 
25·803
63·0
64·0
65·3
65·8
67·0
67·2
62·0
61·5
55·3
52·8
51·9
51·2
49·6
56·6
50·8
50·5
  8·7
11·2
13·4
14·6
17·4
10·6
11·2
11·0
·772
·690
·638
·620
·560
·708
·690
·692
Sky cloudless.
Wind N.E.


 


 

Silchar (Cachar). Elev. 116 feet, Lat. 24° 30′ N., Long. 93° E. (approximate)

 

NOVEMBER 26TH, 1850.   Watch slow 13′ 39″ mean time.

 

Hour Act. Temp.
Act.
Act.
reduced
Barom. Air D.P. Diff. Sat.  
9.11 to 9.24 a.m.
9.34 to 9.41 a.m.
9.50 to 9.57 a.m.
10.07 to 10.14 a.m.
11.03 to 11.16 a.m.
Noon to 12.03 p.m.
12.58 to 1.11 p.m.
2.51 to 3.04 p.m.
3.55 to 4.08 p.m.
4.09 to 4.22 p.m.
4.23 to 4.36 p.m.
19·4
22·7
25·3
26·5
26·3
26·4
27·6
23·0
17·6
15·5
12·0
69·0
81·0
87·5
91·5
89·0
90·0
94·0
93·0
91·5
93·5
93·7
16·4706
16·5937
17·3558
17·5695
17·5251
17·8144
17·9676
15·0880
11·6688
11·0215
  7·8360
 
 
29·999
 
 
29·967
 
29·892
 
29·881
66·3
 
68·7
70·3
73·2
74·5
76·8
78·5
79·5
79·4
78·5
63·5
 
61·5
62·7
60·3
61·7
60·3
62·1
57·0
62·1
62·1
  2·8
 
  7·2
  7·6
12·9
12·8
16·5
16·4
22·5
17·3
16·4
·860
 
·788
·780
·657
·658
·586
·588
·480
·570
·588
Dense fog till
7.30 a.m. Wind
north. Clear.
 
Wind N.E.
Light cirrhus low.
 
Streaks of
cirrhus aloft.
 
Sun sets in hazy cirrhus.


 


 

Chittagong, Elev. 200 feet, Lat. 22° 20′ N., Long. 91° 55′ E.

 

A.—DECEMBER 31ST, 1850.   Watch slow 3′ 45″ mean time.

 

Hour Act. Temp.
Act.
Act.
reduced
Barom. Air D.P. Diff. Sat. Black
Bulb
 
7.39 to 7.52 a.m.
8.40 to 8.53 a.m.
9.04 to 9.08 a.m.
9.52 to 9.56 a.m.
10.02 to 10.06 a.m.
11.16 to 11.29 a.m.
11.52 to 11.56 a.m.
1.38 to 1.41 p.m.
1.47 to 1.51 p.m.
3.10 to 3.17 p.m.
3.18 to 3.25 p.m.
10·0
21·3
23·2
24·3
25·1
24·3
26·6
24·7
25·4
21·1
19·3
70·0
91·5
89·5
87·3
90·5
84·5
92·6
84·0
90·7
86·0
89·3
  8·3700
14·1219
15·6136
16·7341
16·7668
17·1558
17·5028
17·5123
16·8418
14·6645
13·0468
 
29·874
 
29·923
 
 
29·892
 
 
29·831
57·0
59·5
63·3
64·5
65·7
68·5
69·5
71·7
 
71·0
55·7
57·2
59·7
61·3
60·4
58·6
59·2
61·8
 
60·5
1·3
2·3
3·6
3·2
5·3
9·9
10·3  
9·9
 
10·5  
·960
·920
·890
·900
·840
·722
·710
·720
 
·710
 
127·0
 
142·0
148·0
150·0
Cloudless. Mountains
clear. Wind
N.N.E. Cool.
Wind N.W.
 
 
Wind S.W.
 
 
Clouds about
in patches.

 

[ 463 ]

 

B.—JANUARY 1, 1851.   Watch slow 3′ 45″ mean time.

 

Hour Act. Temp.
Act.
Act.
reduced
Barom. Air D.P. Diff. Sat. Black
Bulb
 
7.34 to 7.41 a.m.
8.38 to 8.45 a.m.
9.44 to 9.51 a.m.
10.46 to 10.53 a.m.
11.50 to 11.57 a.m.
12.06 to 12.13 p.m.
12.58 to 1.02 p.m.
1.45 to 1.52 p.m.
3.15 to 3.22 p.m.
4.27 to 4.34 p.m.
4.36 to 4.43 p.m.
4.45 to 4.52 p.m.
4.56 to 5.09 p.m.
5.12 to 5.18 p.m.
10·0
16·0
19·5
21·0
21·5
24·1
23·9
21·4
18·1
10·2
  9·8
  8·5
  5·6
  3·8
69·4
70·0
74·7
78·2
81·2
88·0
87·2
84·5
82·5
82·0
84·0
85·0
85·0
84·0
8·4200
13·3920
15·3660
15·8550
15·6950
16·4603
16·4432
15·0870
13·0320
7·3746
6·9482
5·9670
3·9312
2·6942
29·948
 
29·891
 
 
29·850
 
 
29·798
 
 
 
 
29·778
55·4
58·9
63·2
66·7
69·8
70·3
71·0
71·3
71·3
70·0
 
 
67·5
68·7
54·0
57·7
61·7
62·4
58·3
56·0
56·7
57·5
57·1
59·5
 
 
62·7
62·2
1·4
1·2
1·5
4·3
11·5  
14·3  
14·3  
13·8  
14·2  
10·5  
 
 
4·8
6·5
·953
·970
·960
·870
·688
·625
·625
·633
·625
·708
 
 
·855
·810
 
 
104·5
115·0
120·0
117·0
122·5
 
117·0
Mist rises and
drifts westward
till 7.30 a.m.
 
Wind N.W.,
clouds rise.
 
 
 
 
 
 
Sunset cloudless.


 

C.—JANUARY 2, 1851.   Watch slow 3′ mean time.

 

Hour Act. Temp.
Act.
Act.
reduced
Barom. Air D.P. Diff. Sat. Black
Bulb
 
10.02 to 10.09
10.20 to 10.24
12.03 to 12.10 p.m.
12.22 to 12.25 p.m.
2.04 to 2.08 p.m.
2.10 to 2.14 p.m.
19·2
22·6
24·7
25·9
23·3
23·8
71·0
79·0
89·2
95·5
91·5
93·0
15·8592
16·9048
16·6972
18·6796
15·4479
15·6128
 
29·861
29·858
64·5
65·6
69·0
70·7
71·2
60·6
61·4
59·3
57·5
61·0
3·9
4·2
9·7
3·2
10·2  
·878
·872
·728
·650
·718
116·0
 
119·0
 
112·0
Low, dense fog
at sunrise,
clear at 9 a.m.
Hills hazy and
horizon grey.

Next Appendix L