44 DR. FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XXVI.) 
though we cannot conceive at present that all the particles of the earth contribute, 
as sources, to its magnetism, inasmuch as many of them are diamagnetic, and many 
non-conductors of electric currents, yet it is difficult to say that any large portion 
is not concerned in the production of the force ; hereafter it may be necessary, 
perhaps, to consider certain parts as mere conductors, i. e. as parts merely permeated 
by the lines of force, originating elsewhere, but for the present the whole may be 
assumed, according to the theory of Gauss, as a mighty compound magnet. 
2849. The magnetic force of this great system is disposed with a certain degree of 
regularity. We have the opportunity of recognising it only as it is exhibited in one 
surface, which, being very irregular in form, is always the same to us, for we rarely, 
if ever, pass out of it ; or if we do, as in a balloon, only to an insensible extent. This 
is the surface of the earth and water of our planet. The magnetic lines of force 
which pass in or across this surface are made known to us, as respects their direction 
and intensity, by their action on small standard magnets ; but their average course or 
their temporary variations helow or above, i. e. in the air above, or the earth beneath, 
are only dimly indicated by variations of the force at the surface of the earth, and 
these variations are so limited in their information, that they do not tell us whether 
the cause is above or below. 
2850. The lines of force issue from the earth in the northern and southern parts 
with different but corresponding degrees of inclination, and incline to and coalesce 
with each other over the equatorial parts. Their general disposition is represented 
by the system, which emanates from a globe having within one or two short magnets 
adjusted in relation to the axis. There seems reason to believe, from the analogy of 
such globes to the earth, that the lines of magnetic force which proceed from the 
earth return to it ; but in their circuitous course they may extend through space to 
a distance of many diameters of the earth, to tens of thousands of miles. Messrs. 
Gay-Lussac and Biot, in their ascent in a balloon, perceived some indication of a 
diminution in the intensity of the magnetic force at a height of about four miles 
from the surface ; but we shall shortly perceive that they might be at the time in the 
midst of influences sufficient to account for all the effect, so that none of it might be 
occasioned by removal from the earth as a magnet. The increase of the intensity of 
the magnetic force, as we proceed from the equator towards the poles, accords with 
the idea of the enormous extension of this power. 
2851. These lines proceed through space with a certain degree of facility, of which 
a general idea may be gained from ordinary knowledge, or from experiments and ob- 
servations formerly made (2787.)* Whether there are any circumstances which can 
affect their passage through mere space, and so cause variations in their condition ; 
whether variations in what has been called the temperature of space could, if they 
occurred, alter its power of transmitting the magnetic influence, are questions which 
cannot be answered at present, although the latter does not seem to be entirely 
beyond the reach of experiment. 
2852. This space forms the great abyss into which such lines of force as we are 
