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HISTORY OF ENGINEERING.

Book I.

The Remains of the Tomb of Alexander Severvs show two chambers which containedsarcophagi, and the passages which led to them.

Fig. 232.

Machines and Engines used by the Romans are by Vitruvius divided into three kinds :the scaling machine, constructed for the purpose of ascending without danger, to view worksof considerable altitude, formed of timber, put together by the carpenter, and braced stronglyin every direction. Ladders of all kinds, particularly those attached to the masts of ships,all came under this first denomination.

Machines for lifting stones and heavy weights, employed for the purposes of construction,were made as follows : —

Three pieces of timber, sufficiently strong for the purpose, were connected together at thetop by an iron pin, in such a manner that they could be made to spread extensively at theirfeet : when these were raised by means of ropes made fast at the top, which assisted inkeeping them steady, a block was attached in which were two pulleys, turning on axles, oneabove the other. Over the upper pulley a leading rope passed, which was let fall, andmade to pass under a lower pulley in a bottom block ; it was then returned over thebottom pulley of the upper block ; the rope again descended to the lower block, to the eyeof which it was firmly fastened. The other end of the rope was connected with the axle,which, as it was wound round, elevated the stone or weight to the required height. 'Hieaxie worked in two gudgeons, sockets for which were made in two pieces or elects(chelonia ), affixed to the back of two of the pieces of timber when they were spread out.

Levers, entering mortices, made at each end of the axle, were used to turn it. Ironshears were made fast to the lower block, which opened, and their teeth entered two holescut in the stone to be raised.

A block containing three pulleys was called trispastos; when the lower system had twopulleys and the upper three, pentaspastos ; and when very heavy masses were elevated,longer and stouter beams were required ; the pins which united them at top, as well as theaxle below, were all made stronger in proportion. When used, guy ropes were attachedto the shoulders or top of the three pieces of timber, and if there was no other place con-venient to fasten these to, they were fixed to sloping piles driven in the ground, which werewell rammed round. A block slung to the head of the machine had a rope carried roundit to another block, previously fastened to a pile or stake ; passing over its pulley, it returnedto the block at the top of the machine, round which the rope passed, and descended to theaxle at bottom, to which it was lashed.

By turning the axle with the levers, the machine was used without any danger, the guyropes attached to the piles keeping it perfectly steady.

When heavier weights still were to be raised , the common axle was not strong enough to betrusted; it was, however, retained, but surrounded with a drum or tympanum ; the blocksemployed were constructed after a different manner from that already described ; at bothtop and bottom were two ranks of pulleys, the rope passing through a hole in the lowerblock, so that each end of the rope was equal when extended. It was then bound andmade fast to the lower block, and both parts of the ropes so retained, that neither of themcould swerve either to the right or left. The ends of the rope were then returned to theoutside of the upper block, and passed over its lower pulleys, whence they descended tothe lower block, and, passing round its pulleys on the inner side, were carried up right andleft, over the tops of the higher pulleys of the upper block ; whence descending on theouter sides, they were secured to the axle on the right and left of the drum wheel, aboutwhich another rope was now wound, and carried to the capstan. 'When the capstan wasturned, the drum wheel and axle, as well as the ropes fastened to it, being set in motion,the weights were gently raised, and without danger. Sometimes the drum wheel wasmade sufficiently large to allow men to walk within it, by which means greater power wasobtained than with the capstan.