EARLY MODE OF FEEDING BOILERS. 341 than the cumbrous one to which I have just alluded. At length, however, donkey engines were used, and then came the injector, which, as it possesses no moving parts, and may be worked without the aid of the engine, is, as I have said, generally used (in stopping trains) when the driver is careful, at the very time when the locomotive is not under way. LECTURE II. SELF-FILLING TENDER - STEAM CYLINDERS — PISTONS—CRANKS AXLES -WHEELS- TYRES INDICATOR - -SLIDE VALVE -LINK WE Concluded our last lecture by a description of the various modes which have been employed for feeding the boiler: I will now say a word or two respecting the place whence the feed water comes. You have before you diagrams of three engines: one, of a tank engine, carrying its own water, the others of two engines, each demanding the addition of a tender. Time does not admit of my entering into any description of tenders beyond saying, that they are four or six-wheeled carriages supporting tanks, containing from 1,600 to 2,500 gallons (or even more) of water, and having places for the reception of the fuel; and that, almost invariably, they are fitted with brakes, for which purpose their great weight renders them very suitable. The ordinary mode of putting water into the tender is by means of the well-known water crane; but I wish to call your attention to another mode invented a good many years ago by Mr. Ramsbottom, to whose arrangement of safety valve I have already alluded. By the kindness of Mr. Ramsbottom, I am enabled to show you a model of a tender fitted with his apparatus, and I have hung a diagram (fig. 20) of this upon the wall. The object of the invention is that water may be taken up while the train is in motion; this is a very desirable thing in the case of express trains, such as the Holyhead Mail, where every minute is of consequence, RAMSBOTTOM'S SELF-FILLING TENDER. 343 and a very desirable thing also in the case of slow trains, travelling on a portion of line (such as that between Manchester and Liverpool) where, from its thronged condition, stoppages should be reduced as far as possible. FIG. 20. Ramsbottom's self-filling tender. In arranging for the use of this apparatus, a perfectly level portion of the line is selected, and here there is laid, between the two rails of each line, an opentopped trough, of about a quarter of a mile in length. This trough is kept filled with water from some neighbouring source of supply, and the tender, as you will see, is fitted with a curved pipe projecting forwards and downwards, so that its mouth may dip into the water. As the train goes along the water mounts the curved pipe and overflows at the top into the tender, filling it up to the desired point in this manner 2,000 gallons of water may be delivered into a tender in less than one-third of a minute. The pipe has a joint in it, so that it can be raised when the engine is not over the trough, and lowered when it is. It may perhaps occur to you that there would be a risk of the driver not lowering the pipe, and of his not raising it again, at the proper times, and that thus a portion of the length of the trough might not be utilised while the engine was passing over it; and also, that if the pipe were not raised in time, or were lowered too soon, the ends of the trough might be knocked out, or the pipe might be broken. But this difficulty is guarded against by a very simple but ingenious arrangement. At the ends of the trough the rails are raised a few inches above the general level, there being an incline on each side of the raised point, leading up to it, and down again-that is to say, there is a gentle hill in the rails opposite each end of the trough. You will see, therefore, that it is perfectly possible for the pendant pipe to be lowered before the engine arrives at the trough. The hill raises the pipe so as to carry it clear over the trough end, and then the tender running down the hill plunges the mouth of the pipe into the trough, it may continue unlifted during the entire passage of the tender over the trough, and beyond its further end; because the second hill again raises the pipe, and enables it to escape above the closing end of the trough. Having now dealt with the subjects of the generation of steam, the feeding of the boiler and the provision of POSITIONS OF STEAM CYLINDERS. 345 water, we may profitably consider the engine which utilises the steam that is generated. In ordinary locomotives there are always two complete engines coupled to one shaft, and these engines (as I have already said) operate upon the driving axle directly, without the intervention of gearing. The steam cylinders may be taken as ranging from 14 in. to 19 in. in diameter of bore, and the piston stroke as varying from 20in. to 28 in. The parts of a direct-acting steam engine are few and simple; they comprise the truly bored cylinder, within which the piston moves backwards and forwards under the alternating reversed pressures of the steam; attached to the piston is the piston rod, issuing steam-tight through a stuffing box in the cover of the cylinder; this rod carries at its hinder end a head or crosshead, from which proceeds the connecting rod, that in union with the crank converts the reciprocating motion of the piston into the rotary motion of the crank shaft. To these parts must be added the guide block at the piston-rod head; this block prevents the resolution of the force transmitted by the connecting rod (while it lies at an angle) from deflecting the piston rod, which it would do were not some species of guide provided. The only remaining parts are those of the apparatus which admits the steam alternately on each side of the piston, and also permits the steam which is being used to exhaust alternately, from each side of the piston, and to find its way up the blast pipe into the atmosphere, or to the feed-water tank. 6 In designing the engine of a locomotive the first question to be answered is, Where shall the cylinders be placed? Inside,' that is to say, between the two wheels of a pair, as in the goods engine (fig. 8), or outside,' that is to say, exterior (so far as regards the centre lines of the cylinders) of the two wheels of a pair. The temptations to |