598

HISTORY OF ENGINEERING.

Book I.

In the preceding table is shown the length, total sum expended, cost of workingfor six months, and the returns for the same time upon forty-five of the principal railroadscompleted; and as the works upon them were mostly of a similar kind, it was deemedadvisable to reserve the descriptions which relate to the detail to that portion of the volumedevoted to theory and practice. The various locomotive-engines, the different forms ofthe rails, and the machinery, is described under the separate heads of machines and theirmovers. For the construction of these railways the civil engineer and architect havecontributed their labours; for the machines and engines afterwards applied to it, we areindebted to the several manufacturers now established throughout England. By the unitedlabours of the civil and mechanical engineers a new era has opened upon us, whicheventually will lead to the most l>eneficial results.

Afrnospheric Railway. — Dr. Papin exercised his skill in attempts to derive mechanicalpower from the motion of a piston in a cylinder, and thus produce a vacuum. He firstmade his experiments with gunpowder, and afterwards with steam ; he placed a cylindercontaining a little water and a piston over a small fire; as soon as steam was created thepiston of course rose, and after the fire was taken from under it the steam cooled down,and the piston again descended. Papin, however, applied his discovery, if it might be sotermed, only to mere models; he made no attempt to gain a succession of strokes for hispiston, nor to produce rapidity of motion; he thought it might be so worked, but did notpoint out any method by which it could be performed.

Mr. Valence in the year 1824 was the first to impel a piston through a tunnel, whichhe did at Brighton, and immediately afterwards took out a patent to secure his invention.This was to be applied to the transmission of railway carriages, and the plan consisted ofa series of cylinders of large diameters, within which they were to pass with passengers orgoods being propelled by the pressure of the air upon a disc which was placed in frontof the first carriage: the cylinders were exhausted by air-pumps placed at their ends; theatmosphere then pressing with all its power against the disc, pushed it forwards in thevacuum already produced by the air-pumps.

Mr. Medhurst in 1827 endeavoured to carry out a project he had described sixteen orseventeen years before, as a method of rapidly conveying goods and passengers through atube of 30 feet diameter, by the power and velocity of the air.

Mr. Pinkus in 1834 took out a patent for an extended cylinder or main 40 inches indiameter, with a longitudinal opening along the upper side, through which an arm extendedfrom the piston to the leading carriage, which, with the rest of the train, ran upon the railson the outside of the main. The aperture of the cylinders in advance of the pistons wasclosed air-tight, by a flexible cord which was raised by a grooved wheel in the centreof the carriage, and pressed down by two other wheels at the ends as the train advanced.In front of the piston a partial vacuum was produced by means of air-pumps, andthe atmosphere was supposed to rush into the cylinder through the groove, which waslaid open by the raising of the cord.

Mr. Samuel Clegg , who had been engaged in making some of the arrangements to carryout Mr. Pinkus’s invention at Wormwood Scrubbs, and to demonstrate the principles of thepneumatic railway, discovered that the vacuum might be improved, and in conjunctionwith Mr. Samuda took out a fresh patent. It is now proposed that the moving powershall be through a continuous pipe laid between the rails, and divided by separatingvalves into convenient lengths for the purpose of exhaustion. A partial vacuum is formedin this pipe by air-pumps, which are worked by steam-engines placed at various distances;the separating valves are opened as the train progresses. At the top of the pipe ormain is a continuous groove covered with a valve, made of stout leather riveted betweentwo iron plates, that at the top being wider than the other, to allow of the valve closingand effectually covering the groove; when the valve falls the edge lies upon a compo-sition of bees-wax and tallow, which is passed over by a heater made fast to the frame ofthe leading carriage. The pipe is exhausted in front of the piston, which is attachedto the carriage by a connecting plate, serving to draw the train as well as to sustain thepiston when in motion. This plate has also attached to it a frame on four wheels,which lifts and sustains the continuous valve, whilst the plate is in motion along it; thisis kept open beyond the plate by means of the two outer wheels, and the atmosphere isthus admitted behind the piston. The main or pipe is of iron cast in 9 feet lengths, andput together with socket joints, caulked carefully with yarn and a cement made of whiting,boiled linseed oil, olive oil, or any other, the drying qualities of which are not rapid ;tallow is afterwards used and tarred yarn, to make the joint perfect; the whole is in a softstate, and is not affected by either the contraction or expansion of the metal. The heater,which is described as passing over the valve, consists of a trough filled with charcoal, andat the bottom is a copper blade, which rests on the surface of the composition, and beingalways hot slightly melts it; thus by closing it, the joint is rendered again air-tight as thetrain passes along. The entire main is separated into lengths of 3 miles each, by valveswhich open in a direction to suit the passage of the trains; these valves act in a semi-