Natural PMlor^ophy.'-^Ma^netism and Electi klty. 1 9§ 
MAGNETISM. 
5. Effect of Magnetism on the Balance of Chronometers.^ 
It appears from a curious paper by Mr Fisher, on the Errors in 
Longitude, as determined by chronometers at sea, that a sudden 
alteration takes place in the rates of chronometers^ when taken on 
board of ships, an effect which has been generally ascribed to the 
motion of the vessels. He ascribes the acceleration which takes 
place to the “ magnetic action exerted by the iron in the ship, 
on the inner rim of the balance, which is made of rsteel and 
in proof of this, he found, that analogous effects took place in 
chronometers when under the influence of magnets placed in 
different positions with respect to their balances. Upon the 
whole, says Mr Fisher, it appears that chronometers will he 
generally accelerated (particularly if their balances have not re- 
ceived polarity by the too near approach of any thing magneti- 
cal) on ship-board. It appears probable, likewise, that the 
force of the balance-springs is affected in the same way, since it 
is well known that chronometers having gold balance-springs, 
although more difficult to adjust, yet keep better rates at sea 
than others.” — Phil. Trans. 1820, p. 207. 
6. Diurnal Variation of the Needle.^ <^c . — ^The following in- 
teresting results are ^ven by M. Hansteen of Christiania. 1. 
The magnetic intensity of the earth is subject to a diurnal va- 
riation, decreasing from day-break till 10^ or A. M., when 
it reaches its minimum.^ and from thence it increases till 4^ or 
5^ P. M. It then decreases, and afterwards appears to reach a 
maximum about 3^ A. M. 2. Two or three days after the 
moon crosses the equator, the magnetic intensity seems to be 
weakened. The same happens during an aurora borealis. 
3. 'i'he magnetic intensity is also subject to an annual varia- 
tion, being greater in the winter than it is during the summer. 
4. Every object, of whatever materials it consists, when suspend- 
ed in a vertical position, has a magnetic north pole at its lower 
end, and a south pole at its upper end. 
ELECTJMCITY. 
7. Experiment in favour of me Fluid. — M. Van Marum, in 
.a Memoir, lately read at the Royal Institution of the Sciences of 
