ROMAN.
201
Another machine of an ingenious contrivance, called polvspaston, hut which was onlyused by the most experienced artificers, was a single pole, maintained in its position byfour guy ropes placed in opposite directions. Under the place where the guy ropes wereattached at top, a couple of cheeks were fixed, over which was tied the block. Under theblock was placed a piece of timber, about 2 feet long, 6 inches by 4. The blocks had threepulleys side by side, and three leading ropes were conducted from this part of the machinedown to the lower block, where they passed through its upper pulleys from the side nextthe pole. They were then carried to the upper block, passing from the outer sides of thelower pulley of the upper block. Again descending to the lower block, they passed roundthe second rank of pulleys from the inner to the outer sides, and were then returned to thesecond rank of pulleys in the higher block, over which they passed and returned to thelowest, whence they were again carried upwards, and passing round the uppermost pulleyreturned to the lower part of the machine.
A third block fixed near the bottom of the pole, called artemo, was made fast at a smalldistance from the ground; this had three pulleys, round which the ropes passed for the mento work them, lly this means, three sets of men working without a capstan could raise aweight to any required height.
A single pole was considered most convenient, as there was dispatch and facility in itsuse ; the situation of the weight, whether before it or to the right or left, was of no con-sequence. These machines were generally employed for the loading and unloading ships,and the ships themselves were usually drawn on shore by blocks and ropes only.
Ctesiphon 's method for removing great weights was well known to the Romans andVitruvius tells us that when lie was employed to remove the shafts of the columns fromthe quarry to the site of the temple of l)iana at Ephesus , he did not employ the usualmeans, lest the wheels of the carriages should sink into the soft ground which they had totraverse ; he constructed a frame with four pieces of timber, two of which were the lengthof the shaft of the column, and the other two were placed at the ends as transverse pieces,to secure them together. Iron pivots inserted into the ends of the shafts, run with lead,worked in gudgeons were fastened to the transverse pieces, and the pivots having power toturn freely when the oxen were attached to the frame, the columns rolled round, andwere conveyed the required distance.
Metagenes, his son, adopted the same method to remove the massive entablatures ; heconstructed, in addition to the frame, wheels about 12 feet in diameter, and fixed theends of the blocks of stone into them ; the pivots turning in the gudgeons, when the wheelsrevolved, the blocks remained like axles.
Pajonius attempted to remove from the same quarry a base for the statue of Apollo; thishe placed or rather fitted into two wheels, and round their circumference he attacliedpieces of timber 2 inches square, forming an entire cylinder. A rope was coiled roundthis, and to the end a yoke of oxen was attached ; as the rope uncoiled, the stone by meansof the wheels rolled forward ; but Prconius, who had entered into a contract for its removal,had not sufficient funds to complete the work, much additional labour being required toprevent its swerving from a direct line.
Principles of Mechanics. Our knowledge upon this subject is chiefly derived from\ itruvius, but the study of the mechanical sciences commenced with Archimedes in theschool of Alexandria, established by Ptolemy Philadelphus, and was extended by C’tesibius and Ilero, about 150 years before Christ: these two philosophers first, by an analysis of allthe mechanical engines into their primary elements, reduced the actions of which they werecapable to the combinations of five simple principles, which they called mechanical powers,and their system was known and practised by the Romans as it is by us at the present day.A itruvius explains fully the nature and difference of direct and circular motion, andobserves that rectilinear without circular motion, or circular without rectilinear, are oflittle use in raising weights. He remarks that the pulleys revolve on axles, which goacross the blocks, and are acted upon bv straight ropes which coil round the axle of thewindlass; when that is put in motion by the levers, it causes the weight to ascend. Thepivots of the windlass axle being received into or playing in the gudgeons of the cheeks,and the lever being inserted in the mortice hole prepared for them, are moved in a circulardirection, and thus cause the ascent of the weight. Thus an iron lever applied to a weightmoves what many hands could not do. 'When a lever is placed under the weight upon afulcrum, one man’s strength at the end will raise the weight; this is accounted for by thefore part of the lever being under the weight, and at a shorter distance from the fulcrum orcentre of motion, whilst the longest part, which is from the centre of motion to the head,being brought into circular motion, the application of a slight power to it will raisegreat weights.
When the tongue of the lever is placed under the weight, instead of the end beingpressed down, it is lifted up ; the tongue then, having the ground for a fulcrum, will act onthat, as in the first instance it did on the weight, and the tongue will press against the sidethereof, as it did on the fulcrum, though bv this means the weight will not be so easily