Natural Philosophy. '^Mag^netism. 401 
MAGNETISM. 
5. On the Dip of the Needle and the Intensity of the Mag-^ 
netic Force. — The following observations on the dip of the 
needle and the intensity of the magnetic force, have been col- 
lected and calculated by Professor Hansteen. 
Intensity of the 
Intensity of the 
Dip. 
Magnetic Force. 
Dip. 
Magnetic Force. 
Pep, 
0° 0 
1.0000 
Hare Island, 82® 49‘ 
1.6939 
Mexico, 
42 10 
1.3155 
Davis’ Straits, 83 8 
1.6900 
Paris, 
68 38 
1.3482 
Baffin’s Bay, 84 25 
1.6685 
London, 
70 33 
1.4142 
84 39 
1,7349 
Christiana, 
72 30 
1.4959 
84 44 
1.6943 
Arendahl, 
72 45 
1.4756 
85 54| 
1,7383 
Brassa, 
74 21 
1.4941 
— 86 9 
1.7606 
6. Magnetic Equator. — M. Morlet, in a Memoir on Ter- 
restrial Magnetism, has shewn that the magnetic equator cuts 
the terrestrial equator twice^ and is once a tangent to it. It un- 
dergoes different inflexions, and does not deviate more than 
or 15* on either side of the line. 
HYDRODYNAMICS. 
7. Dr Coate'' s Hydrostatical Balance. — The object of this 
instrument is to ascertain the specific gravity of minerals, &c. 
without the aid of calculation. It is nothing more than a common 
steelyard, ‘the shorter arm of which is undivided, while the longer 
arm has engraven on it a scale, every division of which, reckon- 
ing from the extremity of the steelyard, is marked with a num- 
ber which is the quotient of the length of the whole scale, di- 
vided by the distance of the division from the end. Thus, 2 is 
placed at half the length, 3 at one-third of the length, and so 
on, up to the specific gravity of platinum. When the instru- 
ment is used, any convenient weight is suspended by a hook 
from the notch at the end of the longer arm. The mineral is 
then hung at the other end by a horse-hair, until it is in equilibrio 
with the weight. It is then immersed in water, without chang- 
ing its place on the steelyard, and an equilibrium is obtained a 
second time by shifting the weight ; and when this is obtained, 
the hook of the weight will point out the specific gravity on the 
scale. 
