READINGS OF THE MARINE MERCURIAL BAROMETER, ADIE No. 208, ON BOARD THE YACHT FOX. December, 1857. 29 Inches +. Mean Lat. 740.3 N., Long. 670.4 W.

January, 1858. 29 Inches +.
29 Inches +. Mean Lat. 73°.2 N., Long. 639.7 W.

Inch.

O

42

.381

48

Inch.
.712 45
.380 46

.151

48

*.984 48

*.778

51

*.792 45 *.848

48

.142 47

Inch.
.680 59
.418 60
*.836 59 *.788 63 *.754 63
60 *.856 58 *.946 59
49 .142 47 .172 58 .127 60 .080 60
55 *.966 51 *.982 56 *.986 60 *.974 59
47 *.942 44 .020 52
.078 57 .120 60
.144 52
.141 57
.137 58 .159
.331 55
.377
.612 52 .631 59
.702 56 .712 58 .704 58
.516 48 .626 62 .791 61 1.001 60
1.432 48 1.510 59
1.420 55 1.254 58
.896 49 .844 59 .835 58 .818 59
.690 48 .654 60 .622 59 .647 62
.738 48 .750 59 .762 58 .868 60
1.062 46 1.093
1.098 59 1.081 62
1.002 45 1.080
.798 45 .715
.151
.852 54

23

.266 43

.406 40

.549 53 .448 51 43 .062 48 .070 50 44 .032 42 .125 52 44 .136 42 .300 53

.765 55
.710 55
.313 53
.008 54
.189 52

.450 54

64 0.866 57.4
61 0.677 58.0
62 0.806 56.0
1.068 54.8
61 1.064 54.8
58 0.627 53.5
61 0.311
53 0.710

53.8 51.7

56 0.578 50.7

53 0.361 49.2 53 0.016 50.2

54 0.097 50.0 60 0.383 51.3

1.048

1.624
1.967
1.130

Mean

0.561 47.5 0.556 45.8 0.593

0.593 55.6 0.604 57.4

0.608 58.0

55 0.928 50.3 58 1.374 51.0 61 1.864 52.8 56 1.505 55.0

0.599 59.0 0.587 54.0

READINGS OF THE MARINE MERCURIAL BAROMETER, ADIE No. 208, ON BOARD THE YACHT Fox. February, 1858. 29 Inches +. Mean Lat. 710.5 N., Long. 60°.9 W.

March, 1858. 29 Inches +. Mean Lat. 69.04 N., Long. 590.1 W.

Inch.

1234

.850

48

.868 48

1.154 48

Inch.
.764 50
.898 58
1.252 53

.330 48 .482 52

5

1.438

53

6

1.496

50

1.488 54
1.500 55

7

1.820

52

Inch. .795 58 .874 61 .814 62 1.310 59 1.058 58 .846 62 1.146 6-1 1.574 58 1.542 58 .624 60 1.718 59 1.764 55 1.728 58 1.680 60 1.374 51 1.418 55 1.426 57 1.290 51 1.226 53 1.130 59 .650 56 .580 52 .346 58 *.752 54 *.800 *.907 52 *.950 52 .006 62 .350 50 .352 56 .394 64 .388 60 .430 56 .476 53 .526 56 .630 63 .668 60 .642 47 .670 48 .739 54 .829 58 .875 61 16 .952 50 1.004 57 1.019 58 1.062 58 1.110 58 17 1.090 48 1.096 54 1.120 52 1.108 57 1.103 58 1.042 58 18 .966 50 .896 54 .808 55 .770 53 .748 56 .674 55 0.810 53.8 .628 46 .618 50 .651 53 .668 56 .726 55 .762 59 0.676 .748 47 .718 51 .715 54 .664 59 .619 56 .572 58 0.673 .542 54 .552 54 .540 56 .510 56 .462 56 .418 53 .434 57 .440 57 .404 59 .342 58 0.412 54.8 .725 58 .897 60 1.078 63 1.232 62 0.812 56.8 1.252 50 1.276 52 1.322 60 1.326 60 1.386 65 1.483 58 1.341 57.5 1.282 48 1.242 50 1.280 58 1.271 57 1.322 55 1.358 58 1.292 54.3 1.377 47 1.436 55 1.509 52 1.518 53 1.500 53 1.533 1.479 52.0 1.480 41 1.514 50 1.535 53 1.519 51 1.525 53 1.504 56 1.513 50.7 1.422 46 1.342 48 1.376 49 1.320 51 1.328 51 1.316 42 1.351 47.8 1.362 52 1.415 52 1.449 51 1.448 55 1.449 53 1.410 55 1.422 53.0 1.352 42 1.208 50 1.163 52 1.114 53 1.111 59 1.124 57 1.179 52.2 1.102 49 1.099 51 1.120 49 1.062 47 1.064 52 1.075 53 1.087 50.2 Mean 0.934 48.8 0.971 57.4 0.960 58.1 0.952 55.1

READINGS OF THE MARINE MERCURIAL BAROMETER, ADIE No. 208, ON BOARD THE YAcht Fox.
April, 1858. 29 Inches +. Mean Lat. 740.9 N., Long. 68°.8 W.

FIRST YEAR.-RECAPITULATION OF MEAN. READINGS FROM THE PRECEDING RECORD OF THE ANEROID
BAROMETER, No. 17701, from September, 1857, to September, 1858.

AVERAGE.

N. Lat. W. Long.

1857. 2h. 4h.

750.3 650.0 Sept.
75.2 67.9 Oct.
74.8 69.1 Nov.
Dec.

74.3 67.4

73.2 63.7

6h.

க்

6h. 8h. 10h. Mid't. Mean.

Sh. 10h. Noon. 2h. 4h.
29.936 29.925 29.928 29.933 29.946 29.949 29.950 29.951 29.952 29.953 29.954 29.956 29.943
29.944 29.930 29.916 29.924 29.956 29.958 29.961 29.976 29.985 29.993 29.985 29.977 29.959
29.857 29.842 29.840 29.833 29.869 29.861 29.864 29.875 29.888 29.890 29.895 29.887 29.866
29.786 29.765 29.748 29.742 29.769 29.775 29.779 29.791 29.798 29.796 29.794 29.786 29.777
58, Jan. 29.725 29.712 29.702 29.704 29.739 29.745 29.747 29.756 29.764 29.765 29.758 29.753 29.739
Feb. 29.843 29.829 29.830 29.833 29.868 29.871 29.874 29.886 29.889 29.886 29.877 29.861 29.862
March 30.085 30.077 30.073 30.089 30.120 30.118 30.119 30.124 30.119 30.118 30.114 30.101 30.105
April 30.149 30.138 30.137 30.148 30.153 30.146 30.142 30.144 30.154 30.166 30.168 30.164 30.151
68.7 53.7 May
74.6 60.1 June
74.4 76.4 July
73.1 88.5

71.5 60.9
69.4 59.1

66.0 57.7

72.5 65.8

Aug.

...

30.204

30.223

30.005

30.015

29.945

29.961

SECOND YEAR.-RECAPITULATION OF MEAN READINGS FROM THE PRECEDING RECORD OF THE
ANEROID BAROMETER, No. 17701, from September, 1858, to September, 1859.
At Port Kennedy: Lat. 720.0 N., Long. 94°.2 W.

RECAPITULATION OF MEAN READINGS FROM THE PRECEDING RECORD OF THE MARINE MERCURIAL
BAROMETER, ADIE NO. 208, ON BOARD THE YACHT FOX.

The readings are reduced to the temperature 320. The cistern is 4 feet above the level of the sea.

Comparison of the Readings of the Aneroid and Mercurial Barometers.

The preceding tabular results furnish the means of comparing the two barometers, and of deducing a correction to the indications of the aneroid barometer, in order to give the readings obtained from the mercurial barometer, referred to 32° of temperature. This correction is necessarily independent of the temperature, there being no thermometric readings in connection with the aneroid: any constant correction for difference of level between the two instruments is included. The following table contains the corresponding readings at the same days and hours, each being the mean of six observations a day.

Table of comparison of corresponding mean readings of the mercurial and the aneroid barometer, and resulting correction to the latter.

These differences appear remarkably regular, and show that the mean monthly readings of the aneroid may be relied on to one-hundredth of an inch. There appears to be no tendency of a change of ▲ depending on the higher or lower reading of the barometer, nor is there any variation due to changes in temperature. The correction to the aneroid readings to refer them to the corresponding readings

1 The mean of 11 days, from Sept. 20th to 30th.

2 The mean of 21 days, from Feb. 1st to 9th, and from Feb. 17th to 28th.

8 The mean of 16 days, from April 1st to 16th.

of the mercurial barometer is, therefore, -0.22 inches. This quantity, strictly speaking, is composed of two parts; the first, the true index error of the aneroid, and the second, the specific difference of the two instruments in different latitudes, the mercurial barometer (weighing a mass of mercury against a mass of air) being independent of a change of gravity, whereas the aneroid barometer is sensible to any increase of gravity as we proceed to the northern high latitudes. Within the limits of latitudes 66°.0 N. and 75°.3 N. this variation amounts to 0.014 inches; and its greatest difference from the mean, say in latitude 72°.0 N., is, therefore, + 0.008 inches. This quantity being smaller than the uncertainty of the results by the aneroid, I have considered it as a correction that can safely be neglected. The formula b = b15 (1— 0.0026 cos 2 q) shows the variation for any latitude . North of latitude 45° the aneroid gives the higher readings.

45

Resulting mean 4-hourly and mean monthly readings of the mercurial barometer in the months of September, 1857, and February and April, 1858.—The results for these months, given above, require a small correction to refer them from part of the month to the whole month; this was obtained by means of the known aneroid readings for the interval when the mercurial barometer was not read, the index correction — 0in. 22 having first been applied. We find—

Referred mean readings of the mercurial barometer for the full months of September, February, and April, of the first year :

The following comparisons were made for the purpose of ascertaining how near the mean of 6 and 12 observations a day approximate to the true daily mean as derived from hourly observations. The following mean hourly readings, taken for 15 days between January 6 and January 22, 1858, are taken from the record; also the means for 7 days in January, 1859, and for 15 days in July, 1859. (Of these observations I find only the results recorded.)