bb is a short pipe, which is fastened to the cylinders by the flanch, bb; hh is the flanch of the pipe, fastened to the boiler; and these are connected by the two short pipes, cc, and dd, both of which are provided with a globular joint at oo, and ii. To compensate for any horizontal motion, or any lengthening or shortening of the coupling of the two carriages, the pipe, dd, is enlarged in diameter at d' d', leaving a space between it and the pipe, c c, which is filled with hemp packing. A gland, nn, working in the usual way, is screwed upon this packing, keeping the joint steam tight, and allowing a horizontal motion, or lengthening, or shortening, of the pipe, when necessary. To allow of a circular motion, the end of the pipe, cc, at o o, is globular, and also the end, ii, of the pipe, dd; the ends of the pipes, bb, and hh, have a vertical flange, to which are screwed the rings, 22 and 3′ 3′; these rings are not, however, screwed close to the flanges of the two pipes, hh, and bb, but a space is left of about two inches, as shewn at vv. Within this space, metallic ring packing is laid, which is screwed down upon the outside of the globular end of the pipes, by the screws, pp, and thus forms a steam-tight joint; and the circular or globular end of the pipes, o o, and ii, allows of a motion in any direction, the same as in a ball and socket joint. The end, vv, shews the space, without the packing, and the end, oo, with the packing, screwed down by pp, and in contact with the pipe.

It being of great importance to the perfection of this plan of engine, that the teeth of the wheels, G, and F, should work smoothly, and without jarring or shaking; Mr. Harrison has adopted a plan to tighten the teeth, in case they become loose by being worn, and especially to counteract the effect of what is called the "back lash" of the teeth, in a change of motion, or to prevent

the shock occasioned by any play in the teeth, when the motion is reversed. To accomplish this, Mr. Harrison adopts a double row of teeth, as shewn in Figs. 10 and 11; gg being one of the sets of teeth, and mm the other. b is the axle, upon which the wheel or pinion, F, Fig. 7, is fixed. But, it will be observed, that one only of the breadths of teeth is fixed to the axle, viz. that part shewn by mm, m' m', and which is fixed to the axle by the keys, 44, seen also in Fig. 12. The other half of the teeth, g g, is fitted accurately to the part m' m', but it is allowed to move round it, for the purpose of tightening the teeth; and this is done in the following manner. b, Fig. 12, shews the axle; m'm' is that part of the pinion fixed to b, by the driving keys, 44; a tapered key, 1, shewn also at 1 1 in Fig. 11, is fixed upon the part m'm'; two keys 2 2′, and 3 3′, work against the key 11, shewn in Fig. 11; the key 22′ being drawn outwards by the screw 2′, and the key 3 3′ being forced inwards by the screw 3. Both these keys, as will be seen in Fig. 11, are tapered or diminished in thickness, 2′ outwards, and 3′ inwards the part m'm', being fixed to the axle, and, likewise, the key 11, and the part g g being at liberty to turn round. When, therefore, the key 22' is drawn outwards by the screw, 2', and the key, 33', is pushed inwards by the screw, 3', the part gg' will be turned round by means of the fixed key 1 1. This will throw the teeth, gg'a little out of the line of the teeth, m m, and, therefore, prevent any play which may take place by the wear of the teeth; the teeth, m m, working, or being driven by the wheel, G, in one direction of the motion, and the teeth, gg, in the other direction.

;

The wheels w and w', are coupled together, to obtain the adhesion of the whole weight of the carriage, Fig.7; and they are supported by the springs, ss, in the usual way. The water tank, a, is placed under

neath the boiler, and the pump for supplying the boiler, shewn at P, is worked from one of the axles, supporting the boiler carriage, by the cross head, rr'; p being the pipe leading to the boiler.

Besides effecting a slow motion of the piston, at high rates of speed, Mr. Harrison expects, by this plan of engine, to effect a considerable reduction in the annual expense of repairs of the machinery. On examining the account of the repairs of the Stanhope and Tyne railway engines, (notes I and K, Appendix,) it will be seen, that a very large proportion of the expense consists of the labour of taking the machinery to pieces, and replacing it when repaired; and which is occa sioned, almost entirely, by the machinery being crowded into so small a space underneath the boiler. By this plan the machinery is much more accessible, and constantly under the eye of the engine-man; therefore, when any part of the machinery gets out of order, it can easily be replaced; and when repairs are necessary, the whole of the machinery is quite accessible to the workmen. One of these engines, constructed as shewn in the drawing, and another without the cog-wheels, and with the driving wheel, w, ten feet in diameter, have been furnished by Messrs. R. and W. Hawthorn, of Newcastle, for the Great Western railway.

About twenty-four miles of this railway from London to Maidenhead having been completed, on the 1st of June an experimental trip was made by the directors, and several of their friends, preparatory to the opening of that portion of the line, to the public on the 4th.

The engine employed on this occasion was No. 150, Tabie, No. 1. Page 352, to which was attached a train of carriages containing nearly 200 passengers; with this train, the engine performed the journey in 47 minutes,

the distance being 22 miles, which is at the rate of 28 miles an hour. About an hour afterwards another train started, and performed the journey in 44 minutes, which is at the rate of 31 miles an hour nearly. In returning, the time occupied in accomplishing a distance of 21 miles and 2 chains was 35 minutes, which is at the rate of 36 miles an hour.

The railway was opened to the public on the 4th of June, and it is not only creditable to Mr. Brunel, the engineer, but also a proof of the stability of the road, and the perfection of the machinery, that the directors have been enabled to start eight trains in each direction every day, and that these trains perform the journey with the greatest regularity.

We had an opportunity of travelling along the railway on the 5th of June, from London to Maidenhead and back, with one of the regular passenger trains; being the Eton Montem, for the convenience of the public, an extra carriage was attached to the train, which consisted of three first class carriages, each capable of containing 24 passengers; two second class close, and two open carriages, containing from 24 to 30 passengers each; and one open carriage with six wheels capable of holding 50 to 60 passengers. With this train of carriages in which were upwards of 190 passengers we started from London, the following table will show the time of performing the journey there and back :

The average rate of travelling in both directions, in the above trip is about 25 miles an hour, but it must be considered that a great loss of time was occasioned by checking the speed on stopping at the intermediate stations, and again recovering the speed at starting; the rate being upwards of 30 miles an hour, when not checked.

Considering therefore the disadvantages under which the above experiment was made, the number of stoppages, and the short distance, that the engine had also to drag an extra carriage, and that no attempt was made to urge the engine to its utmost capabilities; it appears quite certain that, with such powerful engines, a much higher rate of speed will be accomplished upon this railway, than has hitherto been attained, especially as it did not appear to us that any obstacle existed to the higher rate of speed being kept up without difficulty.