H8 MOTIVE POWER AND DISPOSITION

there must be three ropes, each the whole length of theplane, one for each roller, and one stretched along the lineof the plane, to draw the descending carriages down, calledthe “ tail rope.” The road will consist of three rails, (asat A A) the whole distance, except where it branches into twoseparate roads, (as at B B) in the middle of the plane, forthe carriages to pass each other. The action of this planewill be readily understood. Thus, suppose the sheeves W W,Fig. I. to represent the sheeve at the bottom of the plane,and the train of carriages fastened to the rope D D', at thebottom of the plane, as at D, ready to be drawn up by theengine; the rope which winds round the sheeve will be inthe position shewn in the drawing, and will be stretched thewhole length of the plane, and reach to the summit, whereit is attached to the team of descending carriages. Theaction of the engine is then employed to drag the ascendingcarriages, D, up the plane in the direction D'D, which will,also, pull the rope E' E round the sheeve, and with it thedescending train of carriages down the plane; and whenthe ascending carriages arrive at the top of the plane, thedescending train will have arrived at the bottom, at E. Whenthe ropes are disengaged from the carriages, and fastenedto those which have to traverse the opposite direction, therope E' E is drawn, in its turn, up the plane, with theascending carriages, by the engine, and the rope D' D thusdrawn down with die descending carriages.

No. 4.—No. 4 is only an extension of this when the sheevewould be placed nearer each other, and the engines at theextremity of the respective planes. In traversing a country bymeans of a series of these double planes, the ropes employedwill necessarily be three times the length of the line of road,though more than what is equal to twice the length is neverin action at one time. If a descent occur in the line whenthe gravity of the carriages are capable of dragging the ropeafter them, then the tail-rope and sheeve may be dispensed