THE

THE COLUMBIA RAIL-BOND.

HE COLUMBIA BOND consists of three parts, two copper thimbles and the

connecting copper rod.

each end of this copper rod is

a truncated cone

head with a fillet

outside is slightly tapered in the opposite way.

In applying the bond, the cone-shaped heads are placed in the holes in the rail from one side and the thimbles are slipped over them from the other.

A portable hand-press is then applied, and the wedgeshaped head of the bond is forced into the thimble so that it is not possible to see the line separating the thimble and the head in a cross-section of the two.

The end of the head of the bond is expanded by a center-punch, held in position in the press.

When installed, owing to the pressure exerted between the head and the thimble, and also to the fact that they are of the same kind of metal, the two become one, both electrically and mechanically.

The contact of rail and bond is made by a wedge expanding the thimble against the hole in the rail, and, as the bond is wedged both ways, it cannot get loose.

For a 0 000 B. & S. G. or 000 B. & S. G. bond, the holes in the rail should be 3-inch, and for a 00 B. & S. G. or a 0 B. & S. G. bond, §-inch.

The total length of a bond is 34 inches more than the distance from center to center of holes in rails. The total length of a bond should be 8 inches more than that of the splice plate.