ENGINEERING. 



287 



some places as much as 4 feet below the low- 

 water mark of the spring tide, and is nowhere 

 uncovered before half tide ; it is also a position 

 much exposed to storms. The new tower will 

 be much larger than Smeaton's, but of the 

 same general form. The base, however, will 

 be made perfectly cylindrical, 44 feet in diam- 

 eter and 22 feet high. The lighthouse proper, 

 resting on this substructure, will be 35 feet 

 in diameter at the bottom, leaving a ledge 

 around it nearly 5 feet wide, which will be 

 used as a landing platform. To the height of 

 134 feet above the rock the tower will taper 

 till its diameter is 18 feet, and above that it 

 will curve outward again, until it is 23 feet in 

 diameter at the top, 8 feet higher, or 142 feet 

 above the rocky base. It will be built of gran- 

 ite,, dovetailed and cemented together, like the 

 old tower. The old lighthouse is 34 feet in 

 diameter at the base and 15 feet at the top, 

 the gallery being 61 feet above high water, 

 and the light 68 feet. The new light will be 

 55 feet higher than the old one. The estimated 

 cost is 70,000. The amount of granite used 

 will be 69,500 cubic feet. The weight of the 

 structure will be 5,200 tons, or nearly 3 tons 

 of insistant load to every square foot of foun- 

 dation. The walls of the hollow portion of the 

 shaft will be 8 -J- feet thick at the bottom, and 

 2J- feet at the top. 



The breakwater built at the mouth of the 

 river Tees, in England, for the conservation of 

 the river, extends from the point at the south- 

 ern side of the estuary for 2| miles in a north- 

 westerly direction, in a line which is almost 

 straight. The work was commenced about fif- 

 teen years ago. About three fifths of the length 

 was successfully built with furnace slag, which 

 was simply tipped, forming a great embank- 

 ment. Beyond that distance the sandy tongue 

 which afforded a foundation for the embank- 

 ment came to an end, and the slag, which was 

 mounded up in the outer waters, was broken 

 into small fragments and washed up by the 

 action of the winter storms each year. The 

 plan was accordingly adopted three years ago, 

 on the advice of John Fowler, of Stockton-on- 

 Tees, of constructing an outside wall of con- 

 crete backed up by a heavy bank of slag. The 

 concrete wall is 19 feet broad at its base and 

 10 feet at the top. A staging built over it sus- 

 tains a tramway of the endless-wire system, on 

 which the concrete is brought out in tubs, 

 while the piles which support the railway are 

 boarded in by stout planks and the interstices 

 calked with oakum, so as to make a series of 

 water-tight compartments, which are filled in 

 with the concrete. At the bottom Roman 

 cement is employed, owing to the impossibility 

 of excluding the water long enough for Port- 

 land cement, of which the main bulk of the 

 wall is composed, to set. The breakwater will 

 be completed, it is expected, in the spring of 

 1880. Its head is to be made circular in form, 

 with a diameter of 100 yards. The foundation 

 of this part will be laid by sinking barges filled 



with slag and large blocks of concrete formed 

 on shore and floatad out on pontoons.... On this 

 foundation the head is to be built of concrete, 

 and will support a lighthouse. A similar 

 breakwater will be carried out from the oppo- 

 site shore. It will extend in an easterly direc- 

 tion about one mile, and will terminate like 

 the other in a circular head and lighthouse. 



The dock at Bristol, in the mouth of the 

 Avon, completed in 1877, after nine years of 

 labor, is 1,400 feet in length and 500 feet in 

 width, affording a water area of about 16 acres 

 and a length of quay of 3,200 feet. The en- 

 trance to the lock from the river Avon is 350 

 yards long and 70 yards in average width, with 

 a depth at spring tides of 40 feet. The large 

 quantity of mud washed up by the tides neces- 

 sitated the throwing up of a protective em- 

 bankment during the construction. The wall 

 of the dock is 40 feet high, and the foundations 

 below the dock floor 2^ to 19 feet in thickness. 

 The footings are of lime concrete, the rest of 

 the wall of rubble masonry faced with dressed 

 stone. Over 1,750,000 cubic yards of material 

 was excavated from the basin and entrance, 

 at a cost of Is. Qd. per cubic yard. 



The Huelva pier recently constructed, which 

 forms the terminus of the Rio Tinto Railway, 

 where the ore mined in the Rio Tinto cuprifer- 

 ous iron pyrites mines is transshipped, was 

 built on a rising grade to enable the cars to 

 be pushed up by locomotives to a height where 

 the ore could be dumped into the holds of the 

 vessels. The length of the pier and approach 

 is 2,444 feet, of which 1,900 feet is on cast-iron 

 screw-piles, driven in groups 15 feet apart, each 

 of the 30 groups containing 8 piles and col- 

 umns; the rest is made up of 29 spans of 50 

 feet each. Independent of the piles was a 

 shipping-deck wharf of creosoted wood, Memel 

 fenders, and piles. 



The new harbor at Madras, which is being 

 constructed according to designs by "W. Parkes, 

 will be the first practicable haven for large 

 craft on the whole eastern coast of India. The 

 harbor will be formed by a couple of break- 

 waters carried out to sea and then bending in 

 toward each other, leaving an entrance between 

 their heads 150 feet in width. The area in- 

 closed by them is- about 140 acres ; the depth 

 of water is generally 4 to 7 fathoms. The 

 piers are to be made of blocks of concrete, 

 weighing 27 tons each, placed on their founda- 

 tion of rubble by the aid of a Titan crane. 

 The work was commenced in the summer of 

 1875. In the first year the southwest monsoon 

 washed up the marl surf-bank. The shifting 

 of the sand up and down the coast, caused by 

 the monsoons, was thought to be a fatal ob- 

 stacle to a harbor, but it has been found that 

 this difficulty was exaggerated. An unexpect- 

 ed movement of sand buried the works on the 

 north pier in the spring of 1877. By the mid- 

 dle of 1878 the pier had been carried out to 

 the distance of 700 feet, and there was no sign 

 of further obstacles from the action of the 



