Chap. XIII.

CARRIAGES FOR TRANSPORTING ‘WEIGHTS.

1023

parated at the level of the diameter of the axle, or in the middle, where it is fastenedtogether by iron bolts. The brass which surrounds the axle and is contained within theiron chair is nicely turned, and in the chamber above, which is cast in the chair, the oilis put, which drops over the axle, to destroy the friction ; an inclined lid resting againstthe spring of the carriage allows it to be replenished as often as required.

The carriage spring has its bearing on the chairs, to which it is also attached by an ironbolt passing quite through the chair, and secured at the bottom by a nut : on the plan isshown the grooves which allow the vertical guides to work, that are attached to the outsideof the carriage.

Thus the manner of fixing the wheels of railway carriages is the reverse of those in-tended for the ordinary road, where the wheels revolve on the axle; in the former, theyare guided by the flanches, and as the carriage is not required to turn, it is securelyfixed to it.

The bearing of railway carriages, on which the axle turns, in common waggons is placedwithin the wheels when they are outside the framework ; in those constructed latterly uponan improved plan, the bearings are on the outside of the wheels, so that a greater width offramework is acquired, as well as elevation above the wheels, which raises the centre ofgravity. The springs, which are made long and straight, are all placed above the frame, sothat the platform, which receives the load, need not be elevated to an unnecessary height.

When the bearings in which the axle turns are placed outside the wheels, there is anadvantage over the plan of having the journal or bearing inside, as well as less frictioncreated ; journals of wheels 3 feet in diameter may be reduced from 3£ to inches indiameter, which presents considerably less surface in contact. The journal of the axlerequires to be turned with the greatest care, as any unevenness would produce considerablemischief: at the outer end it should be made a trifle more in diameter, and be providedwith a collar, to prevent the axle from having any lateral movement.

In the nave of the tv heel a square hole is bored to obtain a more perfect fit, and theend of the axle is wedged firmly into it: in all the common carriages the bearings in whichthe axle turns are placed inside the wheels when these are outside the framework, but inthose built upon the improved principle, the bearings are placed outside the wheels.

For lubricating the axle, there is a small box placed directly over the bearing, having asmall hole in the bottom through which palm oil or tallow may run upon the journal whenthe angles become heated; as the contents melt away# fresh ointment, as the mixture istermed, is supplied by lifting up the lid, which is kept closed by a spring whilst thecarriage is in motion.

Buffing Apparatus is composed of round blocks or discs of metal or wood, wlich projectfrom the ends of the carriages, and are commonly covered with cushions of leather ; theyare fixed to the ends of iron rods placed underneath theframing of the carriage and have a free motion inwards, wherethey press against an elliptical‘spring, when they touch orcome into contact with those of the adjoining carriage:whatever may be the number of carriages in a train, thebuffers are all made to stand in a line with each other, sothat whenever any concussion takes place, the shock is con-veyed throughout, and consequently materially lessened in itseffect: the buffers are also made so that the springs serveeither for pulling or pushing the carriages.

Several other kinds have been used, in which chain andscrew shackles keep the heads of the buffers constantly incontact with each other ; and some are furnished with spiralsprings, with an iron rod passing from one end of the carriage-frame to the other, the buffer heads being connected by chains;in such the rod of the buffer at each end passes through ahollow* tube, where it is surrounded by the spring, whichpresses against the tube, but does not enter it.

Air, from its elasticity, has been found to diminish theeffects of concussion when confined in a cylinder, and actedupon by pistons fixed in the place of buffers.

Boats for the 2'ransport of Stone , to form Breakwaters , fyc. &;c.

— Suetonius (in Claud, c. 26.) informs us, that when Claudius built the harbour at Ostia , by throwing out an arm right andleft, in order to form the pier which closed its entrance,he ordered the ship to be sunk winch had brought thegreat obelisk from Egypt , and Pliqy, lib. xvi. cap. 76.,

mentions that it was formed of immense timbers, one of which, a nr, was ot prodigious size,and that nothing ever appeared at sea more astonishing than this vessel, 120,000 bushelsof lentiles serving for its ballast. Granite columns of such dimensions as those which

Fig. 1562.