580 MR. HUDSON’S HOURLY OBSERVATIONS ON THE BAROMETER. 
the standard temperature of 62°, in the fifth volume of the Astronomische 
Nachrichten, have been employed to reduce the results of the observations 
to zero *. The first of these tables is intended for those instruments which 
are not supplied with a brass scale, and has reference only to the expansion 
of mercury. By this table the observations of the Standard Barometer have 
been reduced to 32° F. The second table is intended for those instruments 
which are furnished with a continuous brass scale, the temperature of which 
it reduces to 62° F., (the standard temperature of the English linear mea¬ 
sures,) and the mercury to 32°, as before. The observations of the Mountain 
Barometer have been reduced by this second table. The observations with 
the Water Barometer have been corrected only for the expansive power of the 
vapour in its vacuum chamber at the temperature of the thermometer attached 
to the vernier, by Mr. Dalton’s Table, given in Dr. Henry’s Elements of 
Chemistry, and adapted to the present purpose by assuming the mean spe¬ 
cific gravity of mercury (that of the Standard Barometer) as 13’624. 
First set of fifteen days’ Observations. April 28th to May 10th, 1831. 
Mean Times 
of 
Observation. 
Number of 
Observations 
at each hour. 
Number of 
Interpola¬ 
tions. 
Barometer. 
Attached 
Thermometer. 
Barometer 
reduced to 
32°. 
Difference of 
Barometer 
from Mean. 
Difference of! 
Thermometer! 
from Mean. 
h 
A.M. 9 
m 
0 
15 
0 
inches. 
29-720 
56-7 
inches. 
29-641 
+ •007 
-0-5 
10 
4 
10 
5 
29-718 
57-6 
29-636 
+ •002 
+ 0-4 
11 
4 
14 
1 
29-713 
58-2 
29-630 
-•004 
+ 1-0 
12 
3 
9 
6 
29-710 
58-6 
29-625 
-•009 
+ 1-4 
P.M. 1 
6 
12 
3 
29-708 
58-8 
29-623 
— •011 
+ 1-6 
2 
7 
12 
3 
29-704 
59-0 
29-618 
-•016 
+ 1-8 
3 
0 
15 
0 
29-694 
58-9 
29-608 
-•026 
+ 1-7 
4 
4 
10 
5 
29-694 
58-7 
29-609 
— •025 
+ 1-5 
5 
2 
11 
4 
29-696 
58-2 
29-613 
-•021 
+ 1-0 
6 
3 
9 
6 
29-701 
57-6 
29*619 
— •015 
+ 0-4 
7 
2 
7 
8 
29-708 
56-9 
29-628 
-•006 
-0-3 
8 
2 
9 
6 
29-718 
56-2 
29-641 
+ •007 
-1-0 
9 
2 
9 
6 
29-725 
55-7 
29-649 
+ •015 
— 1-5 
10 
2 
8 
7 
29-729 
55-3 
29-655 
+ •021 
-1-9 
11 
2 
8 
7 
29-733 
54-6 
29-661 
+ •027 
-2-6 
12 
3 
9 
6 
29-737 
54-2 
29-667 
+ •033 
— 3-0 
Mean . 
10 
5 
29-713 
57-2 
29-634 
* I am indebted to the liberality and kindness of Professor Schumacher for fifty copies of these 
valuable Tables, for distribution among such meteorological observers in this country as may feel de¬ 
sirous of possessing them. 
