308

HISTORY OF ENGINEERING.

Book I.

London, and East and West India Companies, and many private establishments for ship-building.

St. Katherine's Docks. A company was incorporated by an act passed 6 Geo. 4. c. 105,and the docks were opened the 25th of October, 1828. The capital raised by sharesamounted to 1,352,800?. and an additional sum of 800,000/. was borrowed on the securityof the works which had been performed; the engineering department was under thedirection of Mr. Thomas Telford , and the warehouses under that of Mr. Philip Hardwick .

WESTERN.

Fig. 308.

ST. CATHERINE.

These docks occupy a space between Tower Hill and East Smithfield, and communicatewith the river by a lock 180 feet in length, and 45 feet in width ; its construction admitsvessels of 600 tons burthen, 3 hours before the time of high water. The depth of water onthe sills at spring tides is 28 feet, at dead neaps 24 feet, at low spring tides 10 feet, and atlow water neap tides 12 feet, Trinity datum.

The area occupied by these docks within the walls is 24 acres, II of which are water ;the two docks communicate with each other by a basin, and are surrounded by wide quaysand lofty brick warehouses, where the goods are at once housed by cranes out of the holdsof the vessels.

Between the docks and the Tower is a wharf, having a frontage towards the river of187 feet.

Before these docks were commenced, numerous borings were made to the depth of40 feet.

The lock entrance, and the sills under the two middle lock gates, are fixed at a depth of10 feet under the level of low water mark of an ordinary spring tide. The vessels passfrom this lock into an entrance basin of about two acres, and thence, through a single pairof gates, 45 feet in width, into the eastern dock, and by similar means into the western,each of which contains nearly two acres.

The bottom of the docks and basin is 4 feet above the outer and middle lock sills, andthe height of the quays is 8 feet above the water in the docks, which is always preserved atthe same level by means of two steam engines of 80 horse power each, which can fill thelock in seven minutes, and the process of lockage may, without affecting the water in thebasin, be continued, as long as there is sufficient depth of water outside the lock gate.

The small area of these docks, and there being but one entrance, suggested the employ-ment of steam engine pumps, as well as the laying the lock sill so much under the level of