To test the accuracy of the work after the bed-piece has been permanently fixed to the boiler, clamp a cylinder to its seat on the bed-piece, and fit a wooden cross (with a pin-hole through its centre) to the bore of the cylinder at its front end; then pass a fine strong line through the hole, and extend it back so that it shall occupy a point exactly at the intersection of the central line of the driver-axle with the vertical plane of motion of the centre of the crank-pin and connecting-rod; draw the line taut and fasten it in this position; then apply callipers or a gauge at the rear end of the cylinder, between the surface of the bore and the line, above and be-low and right and left of the line; and if the cylinder is in line, the four distances will of course be exactly the same. It is essential that the two horizontal distances should coincide exactly, and that the central lines of the two cylinders of a locomotive should be exactly parallel with each other, but for obvious reasons the exact coincidence of the two vertical distances is not essential to the efficiency or correct working of the engine.

Instead of a wooden cross, as above mentioned, a more convenient instrument, made of metal, may be provided, consisting of four bevel gears, A, which serve also as nuts, which work tour sockets, B, with threads cut on their inner ends, all neatly fitted to a light casting, E, having a fine central hole for the line, as shown. A central gear, C, works the four gears, of course all at the same time. Several sets of steel rods, D, may be provided if necessary, of different lengths, and thus render the instrument universal in its application, each set of rods serving for cylinders varying two inches, more or less. in the diameters of their bores.

To determine whether a cylinder of an old engine is in line: Remove the front head of the cylinder, the piston, the stuffingbox gland, and the cross-head; apply the cross and line, as above directed, extending the line through the piston-rod hole in the rear head to a point exactly central with the crank-pin when the crank is at its dead point; draw the line taut, and, if the cylinder is correctly in range, the line will occupy a central position in the stuffing-box, which maybe determined as before directed. If the cross-head guides are parallel with the line, both vertically and laterally, they are also correct.

Placing Locomotive Cylinders In Line