the Magnetic Poles of the Earth, SS3 
to navigation, it acquires a still higher from the light which it is 
probable it will yet throw over the whole of science. The in- 
terior structure of the earth, it is beyond our power to examine 
with the bodily eye. The greatest depths to which we are able 
to descend beneath its surface, are almost nothing compared 
with the diameter of the earth. In the mean time, the opera- 
tion of the powers of nature on the surface of the earth, discover 
its interior. Thus, the deviation of the plummet from a verti- 
cal line in the neighbourhood of high mountains, from the at- 
traction of the mountain to the plummet, shews, that the mass 
of the earth, taken as a whole, is about five times heavier than 
water, heavuer also than most species of stones, and in all proba- 
bility, therefore, the greater part of it composed of metallic sub- 
stance. In the same manner, the yearly and daily periodic 
motions of the magnetic needle, are a mute language, revealing 
to us what is going on in the bosom of the earth. The aurora 
borealis, too, is probably the result of a struggle of powers 
put in activity by the variously constituted substances compos- 
ing the mass of the earth, which we may thus perhaps one day 
learn to know ; for, to advance from effects to causes, is the na- 
tural progress of science. 
Although the answer of the questions on this subject seems 
thus to have both a theoretical and a practical interest, it is not 
every one’s affair to engage in extensive mathematical investiga- 
tions. I have therefore thought that I might perform a task 
acceptable to a number of the readers of this Journal, in giving, 
in as popular a manner as possible, a statement of the most im- 
portant results of my researches with regard to the Magnetism 
of the Earth. 
The two charts which accompany this paper are two seg- 
ments of the surface of the earth, from the poles to latitude 
50°. The longitudes are reckoned from the meridian of the 
Observatory of Greenwich, as most of the sea observations were 
made by English navigators, who count from that meridian. 
The arrows scattered over the charts give the direction of the 
magnetic needle ; the end next the poles marks the place of ob- 
servation, the angle which the meridian forms with the arrow. 
* These will be given in a future Number. — Edit. 
