All About Engines

The Locomotive 259 the link in mid-position neither eccentric is opera- tive. In intermediate positions of the link the valve is moved, but has a shorter stroke ; cut-off and release are therefore earlier; the engine uses less steam but produces less power. The Modern Locomotive Nothing illustrates so strikingly the increase in size of the locomotive as the accompanying Fig. 145 The Great Bear ” Fig. 145.—Stephenson’s “Locomotion,” a “Stirling Single,” and “The Great Bear” to the same scale copied from Mr. C. Edgar Allen’s book on “ The Modern Locomotive.” Here we have, drawn to the same scale, the “ Locomotion ” of 1825, a Stirling’s “ Single ” of 1870, and the G.W.R. “ Great Bear ” of z9°5- The first named had cylinders of 10 inches bore, and not much smaller than the 15-inch by 26- inch cylinders of the “ Great Bear.” But whereas the steam pressure used in the former engine was only 25 lb. on the square inch, in the latter it was 225 lb. Moreover, the “ Locomotion ” had only two