10 Lovering and Bond on Magnetic Observations at Cambridge. 
with the Gauss Magnetometer, I shall pass at once to them and 
leave the description of the rest of the buildings and the instru- 
ments placed in them for the close. 
The plan of magnetic observations, recommended by the Royal 
Society and generally adopted at the magnetic Observatories, pre- 
scribes that the Declination Magnetometer, and the Horizontal and 
Vertical Force instruments, shall each be observed once every two 
hours during the 24 hours on every day of the year; that is to say, 
one of them is read 2™ 30° before each even hour; one at the even 
hour, and the third 2” 30° after the even hour. One day in each 
month has been set apart for observations of the three instruments 
at shorter intervals. On these days, which are called Term-days, 
the Declination Magnetometer is observed every five minutes, and 
the other instruments every 10 minutes, making four separate ob- 
servations every 10 minutes, or 576 in the day. A short descrip- 
tion of the instruments by which these observations are made is 
promised at the end of the paper. They have but recently been 
received and adjusted, and regular observations were made for the 
first time with them on the Term-day of March, 1841. 
The observations with the Gauss Magnetometer, which make the 
subject of this article, have been coincident in time with those taken 
with the Declination Magnetometer at the British stations and are 
therefore comparable with them. The Report of the Royal So- 
ciety on this great Magnetic Adventure provides that the observa- 
tions shall be made as closely as the nature of the instruments, with 
all the recent refinements of mechanical skill added to the ingenious 
artifices of the observer, will permit; and the time is to be careful- 
ly noted after having been determined by the assistance of astro- 
nomical instruments, so as to make the observations at the different 
stations in a practical sense simultaneous. Observations, according 
