Oliver Evans' America the idea of applying- steam to locomotion was seriously proposed by Oliver Evans, who is generally credited with the invention and introduction of the first successful pressure steam-engine. His application to the Legislature of Pennsylvania in 1786 for a patent covering the adaptation of the steam-engine to driving mills and to the steam-carriage, was refused, but in the following 3-ear a similar application to the State of AIaryland was granted. In 18or, lie built a steatn dredging-machine on an order from the authorities of the city of Philadelphia. This he fitted with wheels connected with the en gine, and, though it was set upon wooden axles, he conveyed it through the streets of the city, a distance of a mile and a half, to the place of launching, in the river Schuylkill. A picture of this historic craft is shown on Plate 22 (fig. 2).
Trevilhick's First first practical locomotive to run on rails or trains was built by Trevithick and Vivian for a railroad at Pen-y darran, in Wales. This was in the year 18o4. The engine was of the high-pressure, non-condensing type, and exhausted into the chimney. On its trial-trip it drew a load of ten tons at the rate of five miles an hour. A picture of this machine is shown in Figure 3. It has been asserted that Trevithick's engine had cog-wheels and ran on a rack-rail, but there is abundance of evidence showing that this was not the case. An eye witness, in describing its performance, says, " Lightly loaded, it did very well upon a level surface or moderate grade, but, more severely tasked, the wheels would sill) round without advancing." In his knowledge of the fact that sufficient traction could be obtained from the adhesion of a smooth snrface wheel upon a smooth rail, Trevithick appears to have seen more clearly than others who succeeded him.
Blenkinsop's a number of years after this partially successful experiment the attention of inventors in their efforts to improve upon Trevithick's engine was directed toward overcoming an imaginary difficulty—namely, that the friction of smooth wheels upon a smooth track would not afford traction sufficient to haul loads of considerable weight. Blenkinsop, for example, in ISii, built a locomotive for the Middleton col liery which was provided with spur-wheels working into a toothed rail or rack on one side of the track. This system was in service for a number of years on a colliery railway between Leeds and Middletown, a distance of three and one-half miles, over which it is reported to have hauled trains of thirty tons' weight at the rate of three and three-quarter miles an hour 22,fig. 6).
Haley's this time, also, Hedley built an eight wheeled locomotive, the wheels of which were driven by gearing to obtain increased tractive adhesion.
"Puffing in 1812, seems to have been the first to real ize the significance of the early experiment of Trevithick with smooth wheels on a smooth track. In that vear he built an experimental carriage the wheels of which were turned by men stationed at four handles. This lie attached to trains of coal-wagons, and, weighting it with varying weights, and at the same time varying the load to be hauled, he deter mined by repeated experiments that by the proper proportioning of the weight upon the driving-wheels to that of the load sufficient tractive adhe sion could be obtained upon a smooth rail without the auxiliaries of spur wheels and racks. Having determined this important fact, he proceeded in 1813 to build a locomotive to haul the coal-trains at the Wylam colliery. This engine had four smooth driving-wheels adapted to a smooth rail. Its boiler-power was found to be inadequate, and this defect was corrected in a second and larger one. This engine had a wrought-iron return-flue boiler, and had eight driving-wheels coupled together by intermediate gear-wheels on the axles, and all propelled by a gear at the centre, which was driven from a walking-beam by the intervention of a connecting-rod and crank. This engine hauled eight loaded coal-wagons at the rate of ten miles an hour. The exhaust was led into the chimney, and the open ing of the exhanst-pipe, the end of which was turned upward, was con tracted, by which means the blast was intensified. " Puffing Billy " 22, fig. 7), as Hedley's locomotive was called, continued in use at the Wylam colliery for many years. In 1862 it was removed to the British Patent-Office Museum, in London, where it is preserved as a memorial.
Brunton's other constructions remarkable to-day as curiosities was a locomotive devised by Brunton which was propelled by two jointed rods or movable legs, in itnitation of the action of the hind legs of the horse.
Stephenson's Stephenson built f6r the Stockton and Darlington road three locoinotives which on trial exhibited consider ably greater merit than any that had hitherto been designed. They weighed about eight tons each. The boiler was provided with a single straight flue. The cylinders of the engine were vertical, and were coupled directly to the driving-wheels. They had two pairs of drivers coupled by horizontal rods; they used a forced draught. At the trial of the " No. " engine of this type (pi. 23, fig. 3) on the opening-day it drew ninety tons at the rate of twelve miles (and at times fifteen miles) an hour.