11. "In combination the wire A3, the rails B3, B3, and the rivets a3, a3, the whole arranged substantially as described for the purpose of securing electrical continuity between said rails."
The above is believed to be the first disclosure of means for electrically connecting rails by a bond wire in any patent, although Robinson had disclosed it to various parties, and used it on installations years before.
On the subject of rail bonding the following bit of evidence may be of interest:
In a letter dated Baltimore, October 29, 1874, addressed to Mr. Robinson by Mr. J. H. C. Watts, of Watts & Co., manufacturers of Robinson's signal apparatus, he says:
"Am afraid your idea of soldering a strip of copper to the rails will prove very troublesome in carrying out, as it is a most difficult matter to heat so large a body of iron sufficiently to make a sure joint such as you require, or that will stand the jarring of passing trains, &c., to say nothing of sneak thieves who abound wherever copper is lying around loose. I know however you scoff at theory so will 'dry up.'"
The electric dynamo of today has removed the above pointed out difficulty. Bond wires or strips are now welded to the adjacent rails for the purpose of securing reliable electrical connection between them. Welding is soldering, according to the definition of the term. Thus, the Encyclopedic dictionary gives the definition: Solder: "To unite or cement together in any way. * * * In autogenous soldering the two pieces are directly united by the partial fusion of their contiguous surfaces."
Thus, more than thirty years ago Robinson proposed to solder bond wires or strips to the rails for the purpose of securing good electrical continuity between the same. But it became necessary to wait some twenty years for the development of a commercially practical process for accomplishing this result. This is found in the modern electric welding process.
Robinson's object was to secure a perfectly homogeneous joint or connection between the bond and the rail. His invention, in this connection, consisted in a metallic bond arranged for electrically connecting adjacent rails of the track and means for forming a homogeneous connection between the bond and the rails. This embraces any mode of accomplishing that result. Robinson had simply anticipated the electric process by some twenty years, but that process now accomplishes the result in a simple manner impossible thirty years ago.
The splice bars now welded to opposite sides of street rails in many places are used primarily for the purpose of electrically bonding the rails; incidentally they serve the double purpose of also making a good joint mechanically. Every electric railroad uses the bond wire or plate in some form, originally invented and used by Robinson, for electrically bonding rails together.
Thus, it is clear, this simple invention of Robinson made more than thirty years ago, an outgrowth of his original creation of the closed rail circuit system, has made possible the electric railroading of today, and the method of rail-bonding is now used on every electric railway using a rail return, throughout the world.