Wooden rails did not, however, entirely and immediately give way to iron rails. On the contrary, the old system was so far maintained that, according to "The Industrial Resources of the Tyne," wooden railways could still be found on the collieries in that district as late as 1860.
Among the advantages derived from the substitution of iron rails for wooden rails was the fact that a horse could draw, on the level, heavier loads than before. On the other hand, the heavier the load the greater was the danger in taking the waggons down hill-sides with only a wooden brake to check their speed; and this danger was increased to an even greater degree when the use of iron rails involved the abandonment of the wooden wheels which had hitherto been retained at the back of the waggons in order that the brake should act more effectively. Still further improvements thus became necessary, and these first took the form of inclined planes on which the law of gravity was employed, loaded waggons raising empty ones, or having their own descent regulated, by means of a rope passing round a wheel at the top of the incline. Later on stationary engines and chains were substituted for the wheel and the rope, horses then being employed on the level only.
Bailey says on this point: "Waggon ways have generally been so contrived that the ascents were not greater than a single horse could draw a waggon up them; but some cases have happened lately where it required more than one horse, and steam engines have been substituted for horses for drawing waggons up these ascents. At Urpeth waggon way five or six waggons are drawn up at one ascent, by a steam engine placed at the top."
Here, then, we have another stage in the process of evolution that was going on. The stationary engine at the top of an incline drawing up, or regulating the descent of, heavier loads, on iron rails, was the first employment on railways of that steam power which was afterwards to develop into the locomotive capable to-day of taking heavy trains at a speed of a mile a minute. In those early days, however, speed was { 209}not regarded as a matter of any importance. Colliery managers were quite satisfied with a steady three miles an hour.