250 On Magnetism. 
Hence it results that the intensity in Dec. 1819 = 1:01912 
. Mar.1820 = 1-01081 
Apr. 1820 = 1-00818 
In the month of May, in which I have not yet completed the 
observations, the force has a little diminished: [ suspect that it 
will increase when the earth shall have passed the aphelion. 
My second magnetic discovery is the following: I have found 
that every vertical body SN, whatever it be, and of any kind of 
matter, has a North-pole at bottom and a South-pole at top, as 
in all vertical bars of iron. 
5S 
SoP—+ 2 5 9}>——+ 1 
d c 
SoP—+ 1 5} —+ 1 
b a 
N 
For otherwise it would be impossible to explain the phenomena 
which I have observed, and which I have determined by a great 
number of incontestable experiments; namely, that the mag- 
netic cylinder oscillates more quickly towards the North in a, 
and more slowly towards the South in 2. And, on the contrary, 
it oscillates more slowly towards the North in c, and faster to- 
wards the South in d. I have found this law constantly con- 
firmed by my experiments near the walls and partitions of houses, 
whether of wood or stone, and even near large trees in the gar- 
dens. This action must necessarily exert. its influence, indeed 
considerably, on, the direction of the compass-needle on ship- 
board. ‘The whole mass of wood in a ship has, in this way, a 
maguetical axis, and the observed variation of the compass ought 
rather to be attributed to this influence than to that of the iron, 
guns, and ballast, carried by the vessel. Hence it results, that 
all observations on the magnetic intensities made within doors 
are uncertain. 
A Table of the actual Intensity of the Magnetic Force in dif- 
ferent Parts of the World, calculated from a great Number 
of Observations, by the ingenious and laborious Professor 
HANSTEEN. (ZACH.) ° 
Places. Dip. Intensity. 
PeUsacacetivee ns: O°. 20) waisiesine a L°COMD 
EERACU ssipia'sias-b:e's.0 42° WO. caseses L'olan 
Paris 
