394 Earthquake. 
place, and the needle will deviate until the repelling power of 
the bar, and the attractice force of the earth on it, are equal to 
each other. This may have set the needle at an angle of 30° 
with its meridian ; then, by approximating the bar, the effect be- 
longing to it will be increased, and the direction of the needle 
will become more oblique. By adjusting the bar in this way, the 
needle may be placed and retained in a position very nearly at 
right angles with its first direction; and then, as the power of the 
earth on the needle increases but very little from the 80° or 85° 
to 90°, and afterwards diminishes, a.small force will make it pass 
the 90°, ard once beyond that point it will continue to move un- 
til its position is completely reversed, 
The time of applying a mineral or other substance supposed 
to contain iron to the needle, is when it is nearly at right angles 
with the magnetic meridian; because an effect will be produced 
there by a force many times smaller than that necessary to pro- 
duce a similar effect on a needle uninfluenced, except by the 
earth’s magnetism. 
M. Haiiy found that in this way effects were produced on the 
needle by bodies that, in common circumstances, appeared to 
have no action, as hematite, the carbonate, phosphate, chro- 
mate, and arseniate of iron, ferriferous carbonate of lime, garnet, 
peridot, &c.; and he observes that this extension of character, by 
means of double magnetism, may be usefully employed in the de- 
scription of ferriferous minerals. 
EARTHQUAKE, 
Inverness, Nov. 12t- 
A smart shock of an earthquake was felt here, and to a con- 
siderable distance round the town, at about twenty minutes pa 
twelve on Tuesday night. It was felt with peculiar violence along 
the banks of Loch Ness. The noise seems to have been greater 
or less, according to local circumstances: in some places it was 
very loud, in others more gentle, but-every where a tremulous mo- 
tion which was for a few seconds communicated to moveables. 
The night was uncosamonly serene, with clear moonlight; and 
while not a breath of wind was stirring on the surface of the 
ground, in the higher regions of the atmosphere the clouds were 
driving rapidly from south to north, Lighter shocks are said to 
have been felt at nine in the evening of Tuesday, and at four in 
the morning of Wednesday. 
Extract of’ a letter, dated Nov ember 11: “ We were visited 
this morning, at 25 minutes before one, with a dreadful earth- 
quake :, being at the time sitting reading, about twelve o’clock, 
I felt the house shake slightly, with a little noise below, which 
put me in a little confusion, as I was well aware that every per- 
son in the heuse was in bed except myself. On feeling this I 
retired 
