ENGINEERING. 



245 



from which the two entrances slightly deviate. 

 The total distance between the old entrance at 

 Blackball Point and the new one at Galleon's 

 Reach, below Woolwich, is two and three- 

 quarter miles. The new entrance joins the 

 docks to the river at its widest part. It is pro- 

 tected by two concrete jetties, opening out- 

 ward, timber leading-jetties ending in curves 

 presenting a wide mouth guiding into the en- 

 trance-lock. The entrance-lock to the basin is 

 800 feet long and 80 feet wide. It has three 

 pairs of wrought-iron gates. The distance from 

 the outer to the inner gate is 550 feet. There 

 is 30 feet of water over the sills at high cide, 

 and any of the ironclads of the British navy, 

 as well as the largest merchant-vessels afloat, 

 can enter the docks. The entrance-basin into 

 which this lock conducts has an area of nine 

 acres. From this a channel, which is 300 feet 

 long by 80 wide, leads into the main dock. 

 This passage has a pair of gates similar to those 

 of the entrance-lock. The main dock has an 

 area of 75 acres, and is one and a quarter miles 

 long. It has a uniform breadth of 490 feet be- 

 tween the copings. On the south side of the 

 new dock are being built two large dry docks, 

 the larger one 510 feet long and 84 feet wide, 

 and the lesser one 420 feet long and 68 feet 

 wide. Their sills are 22 feet below high water. 

 The largest ironclads can be admitted into the 

 first. Beneath the passage connecting the two 

 wet docks the double track of the Great East- 

 ern Railway passes through a tunnel 1,800 feet 

 Jong, the gradients of which are one in fifty 

 from both sides, the level of the track in the 

 center being 43 1 feet below the high- water line. 

 Another double-line railway, as well as a road- 

 way, is carried over the connecting canal by 

 one of the largest swing-bridges yet made. It 

 spans 90 feet, and weighs over 860 tons. The 

 Royal Albert Dock-works are remarkable for 

 the extensive use in them of Portland-cement 

 concrete. The dock-walls of the whole of the 

 main dock and its entrances from the Thames 

 and from the old dock, as well as the two great 

 graving docks, are constructed almost entirely 

 of this material, which was made and depos- 

 ited on the spot. The aggregate length of the 

 dock-walls and the walls to the passages is 

 about three and a half miles. These walls are 

 about 40 feet high, five feet thick at the top, 

 and 18 or 19 feet thick at the base. They re- 

 quired in their construction about 500,000 cu- 

 bic yards of concrete, for which some 80,000 

 yards of Portland cement were used, besides 

 about 20,000,000 brick. Upward of 4,000,- 

 000 cubic yards of material were excavated 

 and lifted an average height of seventeen feet, 

 which was accomplished by steam-excavating 

 machinery of the most advanced types. The 

 steam-navvies used were capable of moving 

 500 cubic yards a day each. The number of 

 steam-engines constantly employed for various 

 purposes was 70, the number of workmen 

 2,000 to 3,000; 43,000,000 gallons of water a 

 day have at times been pumped out. All the 



lock-gates, swing-bridges, cranes, capstans, etc., 

 used in connection with the docks are worked 

 by hydraulic machinery ; and an extensive sys- 

 tem of pressure-pipes and water-mains, with 

 fire-hydrants attached, surrounds the whole 

 dock. The numerous hydraulic cranes are sup- 

 plied with water under high pressure from the 

 pressure-mains through jointed pipes made of 

 gun-metal. The total area of these docks, in- 

 cluding the entrance-basin to the new dock, 

 which can be employed as a landing dock if 

 desired, is about 175 acres. They belong to 

 the St. Katharine Dock Company. There is a 

 complete and direct connection with the whole 

 system of British railways. The transfer of 

 goods to or from the manufacturing districts or 

 the London warehouses is very perfect and 

 economical. The docks will also be largely em- 

 ployed for the transfer of passengers. The 

 cost of the dock extension would have been 

 much greater if the gravel excavated had not 

 been used in making the concrete. The total 

 cost was about 1,000,000. 



The harbor of Holyhead, on the island of that 

 name, adjacent to the Island of Anglesea, at 

 the northwest corner of Wales, is important, 

 as being the regular landing of the Irish steam- 

 ship traffic, lying directly opposite Dublin. The 

 harbor is formed by the great breakwater 

 which was begun by J. M. Rendel. in accord- 

 ance with an act of Parliament passed in 1847, 

 and completed after his death, by Sir John 

 Hawkshaw, in 1873, the plans having been 

 changed and the pier extended so as to inclose 

 400 acres of deep water, in addition to the 

 267 acres of water-space originally intended. 

 The outer end of the breakwater was con- 

 structed with extreme difficulty, owing to the 

 great depth of the water, which was 55 feet at 

 the extremity, and the heavy seas which washed 

 out of place the huge blocks of stone which 

 were employed, and the rubble foundation 250 

 to 400 feet wide. An extension of this har- 

 bor and new landing docks have been dredged 

 out within the shelter of the breakwater for 

 the London and Northwestern Railway Com- 

 pany. The new docks were opened on the 

 17th of June. The railway company com- 

 menced the harbor extension in 1862, adding 

 ten acres to the area of the harbor, and in 1865 

 they built the quay-wall which forms the west 

 side of the new harbor. The quay on the east 

 side was commenced, as the beginning of the 

 extensive improvements just completed, in 

 1874. The harbor, which has been excavated 

 for the traffic of the railway and its sixteen 

 steamships employed in the Irish packet ser- 

 vice, is 2,000 feet long and 600 wide. The cost 

 has been about 500,000. In connection with 

 this large open dock is the graving dock, with 

 an entrance 70 feet wide, a floor 398 feet long, 

 and a depth of 27 feet. 



Important dock and harbor works are being 

 constructed at Milford Haven, South Wales. 

 The docks, which are being constructed after 

 the plans of J. M. Toler, will have an area of 



