1819.1 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



39 



Prince's Channels; the two most frequented passages into the 

 Thames. It stands at the eastern extremity of the Tongue sand, 

 in a depth, at low water, of 17 feet. The foundation is formed of 

 five screw-piles in the form of the letter X, the diagonals being 

 40 feet apart, one being placed at each e.xtremity and one in the 

 centre. These piles are of malleable iron, 6 inches in diameter 

 and 43 feet long. Screws, 2 feet in diameter, were used, and they 

 were sunk to the depth of 19 feet into the bank, which was very 

 hard. The work was constructed after the design, and under the 

 direction of Mr. M'alker, C.E., and stands about 40 feet above the 

 level of low-water spring tides. The method of putting down 

 these piles was the same as that adopted at the Maplin Sand ; but, 

 owing to the greater solidity of the ground, a raft of much greater 

 size and strength was required, to admit of stionger apparatus 

 being used with levers of greater length. The raft required also 

 to be much more securely moored by its four angles, being always 

 in deep water and in a strong tideway. 



In the summer of 1847, the screw-pile was subject to a new trial, 

 in the construction of a pier, or jetty, near the village of Cour- 

 town, about twelve miles south of Arklow, on an open and exposed 

 part of the coast of Wexford. On its commencement, a startling 

 difficulty presented itself. Barges, or strongly-constructed rafts, 

 had been previously found sufficiently steady to act as stages for 

 the workmen, when screwing down either piles or moorings ; but 

 the coast at Courtown being unprotected nearly from north to 

 south, with an open sea of 70 miles in front, a surf of great height 

 and force beats almost without intermission upon the shore, pre- 

 venting the use of any floating body in the construction of the 

 works. As a steady footing for the men is to a certain e.xtent es- 

 sential, it became indispensable that the screwing down of the 

 piles should be effected from the work itself. The method of con- 

 struction that was adopted was very cheap and simple. The piles 

 were to be placed 17 feet apart, in a direct line outwards ; a pro- 

 jecting stage was therefore rigged, extending that distance for- 

 wards, with the other end resting upon and temporarily attached 

 to the solid part of the pier. The screw-pile was then run for- 

 ward upon rollers, lifted by tackle, and placed vertically in the 

 situation it was intended to occupy. A wheel, 32 feet in diameter, 

 formed of capstan-bars lashed together at their ends, ^vith a deejily- 

 grooved end to each, was keyed upon the body of the pile, and an 

 endless rope-band was passed around it, and held in tension round 

 a smaller grooved pulley, fixed about 150 feet back towards the 

 shore. The tendency to pull the pile out of the vertical line was 

 resisted by a guide-pole, with a grooved pulley at its extremity, 

 which pressed against the shore side of the pile. These prepara- 

 tions being made, a number of men hauling upon the endless band 

 gave a rotary motion to the large wheel, and screwed the pile 

 down to its place with great ease. The same operation was re- 

 peated for the next pile laterally, — the cross-beams were laid on, 

 the overhanging platform was pushed forward, and two more piles 

 were inserted. During this time the cross-braces were applied, 

 and the permanent platform was finished. 



The works were by this means conducted with such facility and 

 regularity, that, in spite of rough weather, one bay of 17 feet in 

 advance was generally completed in a day ; and it is evident, that 

 by a modification of the same system, even more could be accom- 

 plished, with greater distances between the sets of piles, if such 

 extension should be considered necessary. 



The new part of the Courtown jetty is 260 feet in length beyond 

 the solid stone part of the old jetty. The main roadway is 18 ft. 

 6 in. wide, with a line of railway laid upon each side, leaving a 

 space for passengers in the centre between the lines. It is ter- 

 minated by a cross-head or platform, 54 feet long by 36 feet wide, 

 with a landing stage at each end, which can be raised or depressed, 

 to suit the convenience of the vessels loading or discharging. 

 Small coUiers, coasting craft, and the largest class of fishing smacks 

 can now receive or discharge their cargoes very rapidly and without 

 grounding. The bottom into which the piles were inserted con- 

 sisted of an average depth of about 8 feet of sand and gravel, upon 

 a firm blue clay. Screws of 2 feet diameter were therefore suffi- 

 cient, with wrought-iron piles, of 5 inches diameter, inserted in 

 the ground to a depth varying between 11 feet and 15 feet. 



The expense of the construction of the extension of this Jetty, 

 including everything, from the screw piles to the finished platform, 

 with the lines of railway, turn-tables, landing-stages, &c., was 

 4,150/., 01 47/. 10s. per lineal yard current. In stating this sum, it 

 must be remembered, that it was the first work of the kind; ample 

 allowance was therefore made for contingencies, and as materials 

 were much more expensive than at present, works of this kind 

 could now be executed at less cost. 



The success attending these applications of the system induced 



its extension to other works, of which it will suffice to mention a 

 few instances, to demonstrate the large field opened for it, not only 

 in engineering works, but for agricultural and other purposes. 



Messrs. Ilansome and May (of Ipswich) have constructed several 

 kinds of cast-iron screw points, shown in figs. 8, 9, 10, and 11. 



Fig. 8. Fig. SI. Fig. lU. 



Weight 3 qr. 22 lb. 



Weight 2 cwt. 3 qr. 141b. 



Fig. 8 shows the largest size, adapted for whole timber piles, 

 which are so often splintered and shattered, and even set on fire, 

 by the rapid blows of the steam pile-driver, when traversing com- 

 pact ground, and where wrought-iron shoes are generally crushed 

 into the timber, even in ordinary ground, with the force of the 

 common pile-engine. The small screw-point opens the way for the 

 conical part, and the larger screw not only draws the pile down, 

 but, when it has penetrated to a sufficient depth, affords an ex- 

 tended base for preventing further depression. Thus several feet 

 of timber must be saved, and the general length of the pile can be 

 reduced, as it will bear a greater weight, and offer a more solid 

 base, when introduced to a less distance than when it rests upon 

 the ordinary sharp wrought-iron pointed shoe. 



Fig. 9 shows the shape adapted for railway signal-posts, and 

 fig. 10 that for the supports for the wires of the electric telegraph. 

 For these purposes the screw points must be very useful, as, inde- 

 pendent of the economy of labour in putting them down by merely 

 screwing them into the ground, instead of digging holes to intro- 

 duce the cross-feet, all possibUity of injury to the banks would be 

 precluded ; whereas, at present, there is always a liability of caus- 

 ing a slip by disturbing uncertain ground, and admitting water in 

 the sides of cuttings. 



The cast-iron screw-socket points (fig. 8) have recently been 

 very successfully applied, for the supporting posts or columns of 

 timber-sheds and buOdings, for railway stations and other pur- 

 poses. These are generally constructed upon made ground, and 

 the foundation for each column is prepared for excavating a hole 

 about 6 feet deep, to be filled with concrete, which is either 

 rammed ro\ind the post, or carries a large stone into which the 

 column is inserted. Or sometimes by having a transverse sill and 

 struts at the foot of the post, which must all be buried in the 

 ground, and be liable to decay from the wet. By the system now 

 introduced, the iron screw-socket alone is inserted into the ground, 

 by screwing it in with capstan-bars; an operation which only oc- 

 cupies a very short time : the earth around is not disturbed, and 

 the timber cannot be exposed to injury or decay. 



As an instance of the stability and the power of holding of these 



