Travels in the Steppes of the Caspian Sea, the Crimea, the Caucasus Part 39

NOTE.

To complete our author's account of Sevastopol, we subjoin an abstract of a paper by Mr. Shears, C.E., which was read at the meeting of the Inst.i.tution of Civil Engineers, January 12, 1847.

"Sevastopol is very peculiarly situated, amidst rocky ground, rising so abruptly from the sh.o.r.e, that there was not s.p.a.ce for the buildings necessary for a dockyard. On account of the depth of water close in sh.o.r.e, and other natural advantages, the emperor determined to make it the site of an extensive establishment, and as there is not any rise of tide in the Black Sea, and the construction of cofferdams would have been very expensive and difficult in such a rocky position, it was decided to build three locks, each having a rise of ten feet, and at this level of thirty feet above the sea to place a main dock with lateral docks, into which vessels of war could be introduced, and the gates being closed, the water could be discharged by subterranean conducts to the sea, and the vessel, being left dry, could be examined and repaired, even beneath the keel. A stream was conducted from a distance of twelve miles to supply the locks, and to keep the docks full; this, however, has been found insufficient, and a pumping-engine has since been erected by Messrs. Maudsley and Field, for a.s.sisting.

"The original intention was to have made the gates for the docks of timber, but on account of the ravages of a worm, which it appears does not, as in the case of the Teredo navalis or the Tenebranes, confine itself to the salt water, it was resolved to make them with cast iron frames covered with wrought iron plates.

"There are nine pairs of gates, whose openings vary from 64 feet in width and 34 feet 4 inches in height for s.h.i.+ps of 120 guns, to 46 feet 7 inches in width, and 21 feet in height, for frigates.

"The manipulation of such ma.s.ses of metal as composed these gates demanded peculiar machines; accordingly, Messrs.

Rennie fitted up a building expressly, with machines constructed by Mr. Whitworth, by which all the bearing surfaces could be planed, and the holes bored in the ribs, and all the other parts, whether their surfaces were curved or plane. The planing was effected by tools which travelled over the surface, backward and forward, cutting each way; the piece of metal being either held in blocks, if the surface was plane, or turned on centres, if the surface was curved. The drilling was performed by machines, so fixed, that the pieces could be brought beneath or against the drills, in the required direction, and guided so as to insure perfect uniformity and accordance between them.

"Travelling cranes were so arranged, as to take the largest pieces from the wharf, and place them in the various machines, by the agency of a very few men, notwithstanding their formidable dimensions; the heelposts in some cases being upwards of 34 feet long. Each endless screw, for giving progressive motion to the cutting tools, was 45 feet long. Some idea may be formed of the manual labour avoided by the machines, when it is stated, that the surface planed or turned in the nine pairs of gates equals 717,464 square inches; and in some cases a thickness of three-quarters of an inch was cut off. The surface in the drilled bolt holes equals 120,000 square inches."

The paper gave all the details of the construction of the gates, and the machinery for making them; and was ill.u.s.trated by a series of detailed drawings.

THE END.