Lovering on Magnetic Observations at Cambridge. 157 
from the following Table, which may be regarded as representing 
the Triple Observations at 2 o’clock, on October 27, 1841. 
1/2|3)/4/5/6|7/8)9 
V.|D.1 H'V.'D.'H.|V.!D.) A. 
In the case of the extra observations, the time belongs, as nearly 
as it could be determined, to the observation which stands beside it. 
One division on the scale of the Declination-Magnetometer 
amounts to .73 of a minute of arc, and one division on the scale 
of the Horizontal-Force Magnetometer amounts to 1.079 minutes 
of are. 
A decrease of numbers on the scale of the Declination-Mag- 
netometer corresponds to an increase of Westerly Declination in 
the marked end of the instrument. 
A decrease of numbers on the scale of the Horizontal-Force 
Magnetometer corresponds to a diminution in the amount of the 
Horizontal-Force Component. 
After the close of the February Term-day, a copper bar was 
substituted for the Horizontal-Force Magnetometer, and the ob- 
servations were continued with that until March 14, when a small 
steel magnet was added to the copper bar. Observations were 
made with this last arrangement until the commencement of the 
March Term-day, when the original Horizontal-Force Magnetom- 
eter was restored. 
The Barometric Observations were made with one of Cary’s 
mountain brass instruments belonging to Mr. W. Cranch Bond. 
The tube of this barometer had a diameter of .17 of an inch. 
The instrument was stationed, according to Mr. Bond’s determi- 
30 
