BAROMETER—THERMOMETERS. XV 
The following are the monthly means of the observations of the balance 
magnetometer for the years 1850, 1851, 1852 :— 
Month. 1852. 
VANUATY alent es 99°8 
Pebruary..) 3.0.05. 108-4 
arekiy “irene : 98-7 
Lprilf Sree. : 91:5 
May . Qe : : 81:1 
dune . Vo. . ; : 89-9 
Thy <2 Uae 96°8 
August, Vee. 91:2 
September . . . : 90:9 
Octoher ie : 88°3 
November .. . 80-6 
December... 70:4 

It appears from the above table that a marked break in the continuity occurs 
between June and July 1851. It seems likely that some unrecorded alteration 
was made on the instrument about that date. (The bifilar was altered July 
8, 1851.) 
It seems advisable, therefore, to divide the whole body of vertical force obser- 
vations now published into three distinct series. The first of these will extend 
from January 1, 1847, to January 18, 1848, the date of the change of plane; the 
second from January 18, 1848, to June 30, 1851; and the third from June 30, 
1851, to December 31, 1855. 
BAROMETER. 
A detailed description of this instrument is given in the Introduction 1845-6, 
p. li. 
All the observations are corrected by — 0:012 inch to the mean of the Royal 
Society’s flint and crown-glass barometers ; they are also corrected for temperature 
to 32° Fahr. by Schumacher’s Tables, given in the Report of the Committee of 
Physics of the Royal Society of London. The cistern of the barometer is 213 
feet above the mean level of the sea at Berwick-upon-Tweed. 
THERMOMETERS. 
A description of these instruments will be found in the Introduction, 1845-46, 
p. lili. In page lv. of the same Introduction we have a table of corrections for 
the readings of the dry and wet bulb thermometers to the temperature by 
MAG. AND MET. OBS. 1847 To 1855. d 
