568 THE POPULAR SCIENCE MONTHLY. 



not far to seek. No matter how commercially lucrative the work upon 

 which he was engaged might be, he would instantly turn aside from it 

 to seize and realize the ideas of a scientific man. He had an inventor's 

 power, and an inventor's delight in its exercise. The late Mr. Becker 

 possessed the same power in a very considerable degree. On the Con- 

 tinent, Froment, Breguet, Sauerwald, and others might be mentioned 

 as eminent instances of ability of this kind. Such minds resemble a 

 liquid on the point of crystallization. Stirred by a hint, crystals of con- 

 structive 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 re- 

 lationship 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 recognize 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 endeavor 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 re- 

 garding 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 afterward reuniting. If the two branch beds be equal in 

 depth, width, and inclination, the water will divide itself equally be- 

 tween 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 sub- 

 division 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 metallic connection being 

 established between the other end of the battery and the gas-pipes 

 under the street. As lono- as the electric main continues unconnected 



