To Trevithick and Vivian, who were engineers at Camborne, in Cornwall, belongs we believe the honour of having invented and carried into practice locomotive engines. This single event forms an era, not only in mechanical science, but also in our social relations; as it is calculated to bring about a more extensive and beneficial change than almost any other event on the page of history, by placing the arts, sciences, knowledge, conveniences, comforts, manufactures, and produce, peculiar to each remote place or district within the reach of all.

We should not omit to notice, that the possibility of applying the power of the steam engine was mentioned by several mechanics, soon after it was brought into a practicable form by Savery, Newcomen, and others, in the early part of the last century; and towards the latter part (1784), the celebrated James Watt mentioned the subject in his specification of that date, seemingly with the view of recording Himself as the inventor; but he never built a steam carriage; and the machine which he suggested under his general patent, was designed for the common road. "A carriage for two persons, might (he observed) be moved with a cylinder of seven inches in diameter, when the piston had a stroke of one foot, and made sixty strokes a minute." In a note to a late edition of Dr. Robinson's mechanical Philosophy, Mr. Watt states: "I soon relinquished the idea of constructing an engine on this principle, from being sensible it would be liable to some of the objections against Savery's engine, viz. the danger of bursting the boiler, and also that a great part of the power of the steam would be lost, because no vacuum was formed to assist the descent of the piston." This extract affords clear evidence of two important facts.

The first, that Mr. Watt did not entertain the idea of applying his crude scheme to railways, although there were many in active operation in the North of England, and some few in Wales. The second fact is, that Mr. Watt acknowledged the incompetency of his own scheme to effect the object designed.

In the formidable qualities which had excited the fear of Watt and others, Trevithick and Vivian perceived those very properties which fitted it to become the actuating principle of their mechanism. Above all other considerations which swayed them in the preference of steam of a high temperature, was the power it gave of dispensing with the use of the condenser altogether; a part which, from its cumbrousness, and the difficulty of supplying it with water, rendered it far inferior even to Newcomen's imperfect apparatus for locomotive purposes.

Being unprovided with an authentic drawing of Trevithick and Vivian's locomotive, we will endeavour to explain its arrangements with such diagrams as we have in our possession. The annexed, we are informed, is a sectional sketch from one of their engines, containing the same leading features as their locomotive.

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At a a is a cylindrical boiler, with a fire door at b, at one end of the cylinder; c c is the fire-place, from which proceeds the principal flue, the parts being shown by dots, as they are supposed to be situated on one side of the vertical plane, through which our section is made; the flue, therefore, is turned at the circle c, then recurved and continued to the chimney^. This arrangement of furnace and flue within the boiler has been ever since distinguished by the name of its inventor, Trevithick, and has been more used than any other, on account of its economy in the consumption of fuel. The lower part of the working cylinder h is immersed in the boiler, and the upper has a jacket, around which the fresh hot steam circulates freely, so that no loss of power can be sustained by the cooling influence of the air upon the cylinder, as was previously the case. Above the cylinder is the four-way cock i, for admitting and discharging the steam alternately; in the latter operation the waste steam was discharged along a pipe, j, into the chimney, which, by increasing the draught through the fire, augments the production of steam, and gets rid of the nuisance ofthe waste steam, in a manner so desirable as to render it now indispensable.

The upper end of the piston rod is furnished with a cross head, which is placed in a direction at right angles to the length of the boiler, and parallel to each other. To the ends of this cross head are joined two connecting rods, the lower ends of which work two cranks, fixed in the extremities of the axis which carries the running wheels, the axis extending across and beneath the boiler, and immediately under the centre of the steam cylinder. This arrangement is shown in Fig. 1 of the following diagrams, extracted from Mr. Gordon's Treatise on "Elemental Locomotion," which states it to be an end elevation of Trevithick and Vivian's locomotive engine; and Fig. 2 a side elevation of the same. Mr. Gordon has, however, omitted the chimneys, and has shown the eduction pipe as discharging the steam directly into the atmosphere.

Fig. 1.

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Fig. 2.

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The next invention which we have to notice, in accordance with our chronological order, is that of an improved cast-iron rail or plate, which has been proved in numerous situations to be highly useful; it was patented by Mr. J. Woodhouse, of Ashby-de-la-Zouch, in 1803. The specification describes various modifications of the plan, showing its application to gravelled roads, paved roads, or streets, and to railways. But the following diagram will suffice to show its application to the latter object, and its adaptation to the other objects may be as readily conceived. At a a is the rail or plate, the upper surface of which is made concave, as shown in the section in Fig. 1. The length of these rails or plates is shown at a a in the elevation Fig. 2, and the mode of supporting and fastening their ends on two bearers or sleepers b b b. The bearings may be made of timber, stone, or cast-iron or wood piles; and the plates fixed by screw or cotter bolts. The road is to be made even with proper road materials, and the rails will then, the patentee states, be immovable. It was likewise intended to use the said hollow rails or plates as water-conduits or gutters, to which object they have been frequently and are now applied in many parts of London and elsewhere.