crystals
of constructive thought immediately shoot through them. That Mr.
Edison possesses this intuitive power in no common measure, is proved
by what he has already accomplished. He has the penetration to seize
the relationship of facts and principles, and the art to reduce them
to novel and concrete combinations. Hence, though he has thus far
accomplished nothing that we can recognise as new in relation to the
electric light, an adverse opinion as to his ability to solve the
complicated problem on which he is engaged would be unwarranted.

I will endeavour to illustrate in a simple manner Mr. Edison's alleged
mode of electric illumination, taking advantage of what Ohm has taught
us regarding the laws of the current, and what Joule has taught us
regarding the relation of resistance to the development of light and
heat. From one end of a voltaic battery runs a wire, dividing at a
certain point into two branches, which reunite in a single wire
connected with the other end of the battery. From the positive end of
the battery the current passes first through the single wire to the
point of junction, where it divides itself between the branches
according to a well-known law. If the branches be equally resistant,
the current divides itself equally between them. If one branch be
less resistant than the other, more than half the current will choose
the freer path. The strict law is that the quantity of current is
inversely proportional to the resistance. A clear image of the
process is derived from the deportment of water. When a river meets
an island it divides, passing right and left of the obstacle, and
afterwards reuniting. If the two branch beds be equal in depth,
width, and inclination, the water will divi de itself equally between
them. If they be unequal, the larger quantity of water will flow
through the more open course. And, as in the case of the water we may
have an indefinite number of islands, producing an indefinite
subdivision of the trunk stream, so in the case of electricity we may
have, instead of two branches, any number of branches, the current
dividing itself among them, in accordance with the law which fixes the
relation of flow to resistance.

Let us apply this knowledge. Suppose an insulated copper rod, which
we may call an 'electric main,' to be laid down along one of our
streets, say along the Strand. Let this rod be connected with one end
of a powerful voltaic battery, a good metal