506 DR. LAMONT ON THE MAGNETIC OBSERVATORY 
taneity could exist between points of the earth’s surface widely 
remote, and in such case the expectations which have been 
formed of the results of corresponding observations could hardly 
be fulfilled. 
Supposing however that corresponding observations would at 
all events find a useful application to theory, it may still be ques- 
tioned whether it would not be more advantageous to choose the 
times of the more considerable disturbances, instead of term-days 
as at present in use. Whilst under ordinary circumstances we 
obtain the total effect of a great number of causes, without being 
enabled to decide what is due to any single cause, disturbance 
observations give us the immediate result of a single determinate 
cause, which result we may follow from station to station, and 
may thus investigate relatively to its origin and extension. 
It being now recognised that the magnetic variations are nei- 
ther perfectly simultaneous nor perfectly similar in their course 
at different places, the question which presents itself is to discover 
where are the obstacles to the simultaneity and similar course, 
and whether the qualities of soil or air have any part therein. For 
this purpose very exact simultaneous observations at points near 
to each other, often repeated and under varying atmospherical 
circumstances, may be advantageous, and with this view observa- 
tions were made simultaneously at Munich and on the Hohen- 
peissenberg on the term-day of September 1841. I hope soon 
to accomplish many similar experiments. 
Without entering further into the results of the observations 
contained in our registers, or the more immediate consequences 
which may be derived from them, I proceed to notice, in the 
briefest possible manner, experiments made with reference to 
the magnetic instruments, and to give the conclusions to which 
they have led. ; 
When the magnetic observatory was first established I fol- 
lowed the principles laid down by M. Gauss, and chose mag- 
netic bars of 25 lbs. weight. The declination bar was suspended 
in the ordinary manner ; but as the mode of suspension of the 
bifilar did not appear to me to offer sufficient security, 1 em- 
ployed as a torsion force, instead of two threads*, a steel spiral — 
spring (an English chronometer spring) in the following manner: 
* Mr. Christie employed fcr the examination of the changes of intensity a 
needle which was kept nearly perpendicular to the magnetic meridian by means 
of two strong magnets. The use of two parallel threads for the measurement” 
of torsion was first introduced, as far as I know, by Mr. Snow Harris, and is de- 
