26 Prof. Henry on Electrical Induction 
there were no bodies in the vicinity to attract it from the con- 
ductor. 
In discussing these, and other facts to be mentioned hereafter, 
we shall, for convenience, adopt the principles and language of 
the theory which refers the phenomena of electricity to the ac- 
tion of a fluid, of which the particles repel each other, and are 
attracted by the particles of other matter. Although it cannot 
be affirmed that this theory is an actual representation of the 
cause of the phenomena as they are produced in nature, yet it 
may be asserted that it is, in the present state of science, an ac- 
curate mode of expressing the laws of electrical action, so far as 
they have been made out; and that though there are a number of 
phenomena which have not as yet been referred to this theory, 
there are none which are proved to be directly at variance with it. 
That the wires of the telegraph should be frequently struck 
by a direct discharge of lightning, is not surprising, when we 
consider the great length of the conductor, and, consequently, 
the many points along the surface of the earth through which it 
must pass, peculiarly liable to receive the discharge from the 
heavens. Also, from the great length of the conductor, the 
more readily must the repulsive action of the free electricity of 
the cloud drive the natural electricity of the conductor to the 
farther end of the line, thus rendering more intense the negative 
condition of the nearer part of the wire, and, consequently, in- 
creasing the attraction of the metal for the free electricity of the 
cloud. It is not however, probable, that the attraction, whatever 
may be its intensity, of so small a quantity of matter as that of 
the wire of the telegraph, can of itself produce an electrical dis- 
charge from the heavens: although, if the discharge were started 
by some other cause, such as the attraction of a large mass of 
conducting matter in the vicinity, the attraction of the wire might 
be sufficient to change the direction of the descending bolt, and 
draw it in part or whole, to itself. It should also be recollect- 
ed, that on account of the perfect conduction, a discharge on any 
of the wire must affect every other part of the connected 
line, although it may be hundreds of miles in length. 
That the wire should give off a discharge to a number of poles 
in succession, is a fact I should have expected, from my previous 
researches on the lateral discharge of a conductor transmitting a 
current of free electricity. In a paper on this subject, presented 
to the British Association in 1837, [ showed that when electricity 
strikes a conductor explosively, it tends to give off sparks to all 
dies in the vicinity, however intimately the conductor may be 
connected with the earth. In an experiment in which sparks 
from a small machine were thrown on the upper part of a light- 
ning, rod, erected in accordance with the formula given by the 
French Institute, corresponding sparks could be drawn from every 
