1016
THEORY AND PRACTICE OF ENGINEERING.
Book II.
paid to the arrangement and material employed for the tackle; ropes have yielded in someinstances to chains, and levers of great length have been applied, and sometimes a series,turning on sockets at one end, have been used, where it has been necessary to multiplypower to any great extent: by the efforts of iron and timber judiciously combined in awell-constructed machine, weights of any amount are now raised with apparent ease andfacility.
M. Lebas, an engineer of the Marine in France , was commissioned in 1831 to bringfrom Luxor in Egypt one of the granite obelisks, and raise it on a pedestal to ornamentthe city of Paris ; it is 75 feet in height, containing about 3000 cube feet, and was estimatedto weigh nearly 258 tons.
The obelisk was cased with timber throughout its whole length; underneath its base, atthe lower side, was placed a wooden roll or cylinder, C, upon which the whole obeliskturned as upon a hinge during its movement: there were five stays on each side, formed ofmasts, one of which is shown at D ; these were all united at their summit between two otherslaid at right angles with them, the whole being bound round with ropes. The ten mastsrested on a level platform, and their ends being rounded, they worked in a hollow channel
BAISING AN OBELISK.
prepared to receive them, and together could be moved upwards or downwards, in themanner of a hinge, so that when the ends at E were pulled down by the ropes of thewindlass attached to them, the obelisk was advanced further into its perpendicular position ;480 artillerymen worked ten capstans, forty-eight being placed to each. Iron chains wereplaced around the top, and four others passed to capstans at the extremity of the inclinedplane, for the purpose of holding the obelisk steady, and rendering its motion regular as itadvanced.
The whole of the operations were admirably conducted, and some improvements wereadopted which we do not find made use of by Fontana; the application of the lever, D,is a decided advantage.