678 
APPENDIX. 
TABLE IV. 
In tlie construction of this table my object was to ascertain the periodical oscillation and mean 
pressure of the atmosphere in the open sea, in different parts of the globe, where the observations 
are uninfluenced by local disturbances inseparable from those made on shore. The observations 
besides possess the advantage of being made with the same instrument, and under similar cir- 
cumstances, in places widely situated from each other, and consequently of exhibiting a relative 
measure free from the inaccuracies which are liable to arise from comparisons of results by 
difterent barometers. I trust that the length of the series has in a great measure overcome the 
irregularities to which such delicate observations are liable on board a ship constantly in motion. 
The instrument used was an iron cistern marine barometer of .lones’s make ; neutral point 
30.102; capacity temperature 52°. It was suspended in my fore cabin, and, with the excep- 
tion of the first five months, registered every three hours, beginning at noon. 
Between the tropics, where the variation of the temperature is trifling, and where the horary 
oscillations are increased, and suffer fewer interruptions from changes in the atmospherical tides, 
I have given the mean altitude for every five degrees of latitude on each side of the equator, and 
in the extra- tropical latitudes to every five or six days. It would have been better, no doubt, 
to have given the results of different parallels throughout ; but the table being differently con- 
structed at first, I did not think it necessary to make the alteration, particularly as the observations 
require to be corrected for temperature ; and in such a series of observations the time that would 
have been necessary for this purpose was more than I could spare to have had the tables ready 
in any reasonable time. Such persons, however, as are curious in this matter can make the cor- 
rections for themselves on referring to the data eontained in this and the following table, or to 
my meteorological journal, which will be deposited in the Hydrographical Office for this purpose. 
NORTH ATLANTIC OCEAN. 
Date. 
Latitude. 
North. 
Longitude. 
West. 
BAROMETER. 
Mean 
tempera- 
ture. 
Mercury. 
A.M. 
P.M. 
Mean. 
3 
9 
Noon. 
3 
9 
Midnight. 
1825. 
June 7- 
— 8. 
— 9. 
— 10. 
— 11. 
_ 12. 
— 13. 
— 14. 
— 15. 
— 16. 
— 17. 
— 18. 
0 ' 
24 8 
21 57 
20 1 
0 ' 
19 21 
21 17 
23 24 
30.140 
.139 
.025 
30.140 
.160 
.093 
30.150 
.160 
.023 
30.180 
.160 
.080 
30.160 
.082 
.127 
30.170 
.136 
.158 
30.156 
.139 
.121 
70.87 
72.40 
7360 
25“ to 20“ 
19“ to 25“ 
30.101 
30.131 
30.111 
30.140 
30.123 
30.155 
30.139 
72.29 
18 37 
17 29 
25 28 
26 59 
.100 
30.250 
30.150 
30.ioo 
30.080 
.048 
30.140 
.140 
30.130 
.197 
30.112 
.130 
74.31 
74.54 
20“ to 15“ 
25“ to 27° 
30.125 
30.150 
.30.100 
30.064 
30.140 
30.113 
30.121 
72.42 
15 36 
13 24 
11 8 
27 39 
47 
18 
30.105 
.020 
.040 
30.070 
.100 
.080 
30.079 
.155 
.130 
30.105 
.080 
.028 
30.135 
.120 
.047 
30.072 
.080 
.080 
30.094 
.092 
.067 
76.40 
76.77 
77-70 
15“ to 10“ 
27“to0 
30.055 
30.083 
30.121 
30.071 
30.101 
30.077 
30.084 
76.95 
8 9 
7 21 
7 2 
6 25 
27 17 
26 39 
25 48 
26 15 
30.100 
.020 
.090 
.021 
30.079 
.068 
.050 
.070 
30.030 
.184 
.T 37 
30.100 
29.920 
.994 
30.090 
30.177 
.090 
.036 
.100 
30.100 
.040 
.020 
.057 
30.083 
.053 
.038 
.079 
78.62 
78.63 
78.29 
79.75 
10“ to 5“ 
27“ to 26“ 
30.058 
30.067 
30.117 
30.026 
30.101 
30.054 
30.063 
78.82 
