1S40.J 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL, 



29 



REVIE'WS. 



Theory, Practice ami Architecture of Bridget. The thonj hy James 

 Hann, nf King's College, and the practical and archilecliiral treatises 

 iy William Hosking, F.S.A., &c., Vol. I. London: John Weale. 



Our present remarks will be confined to Mr. Hughes's paper on the 

 " Foundations of Bridges," as we have previously noticed most of the 

 other articles. Mr. Hughes commences his paper by taking a review 

 of various methods of laying foundations by mean of caissons, next he 

 explains tlie manner of building liridges on dry land, the stream being 

 afterwards diverted from its old course and made to pass imder the 

 new bridge, — he then explains the method of building piers called by 

 (ho French encaissemiiit, practised by Belidor. Afterwards comes the 

 method of laying, in deep water, ioumlations of piers, bridges, &c., 

 without the aid of a coffer dam. As this portion of the paper will 

 best explain the talents and capacity of its author, we shall give a 

 lengthened extract, accompanied by tlie wood engravings, liberally 

 furnished to us by the publisher. 



The first work of the kind I shall describe was projected by Mr. Telford, 

 aiul executed under the suiHriutcndence of Mr. David Ilcniy, at Ardross.in 

 Harbour, in Ayrshire, N. I!. ; and as the mass of stones used in the founda- 

 tion was tliere set in toleraldy regular order under water, without the aid oj 

 coffer-dam, or caisson of any kind, there can be no douljt of the same system 

 being equally jiracticahle in many cases of bridge foundations. 



The stones at Ardrossan were of veiy large superficial (hmensions, varjing 

 from six to ten feet long, and tl\ree to five feet wide ; they were first held 

 fast by an implement, technically called nippers or devil's claws, auti were 

 then lowered by a crane through a depth of six or eight feet of water on to 

 a hard and solid foundation. The lilocks were placed etui to eiul, the i)Osi- 

 tion of the last stone lowered being found by jirobing with a slight iron rod ; 

 and as soon as each stone was in its place longituihnally, the claws were (hs- 

 cngagetl, and the stone allowed to rest upon the course Ijelow, as seen in fig. 

 1. The com'scs were continued entirely througli tlie whole thickness of the 

 l>ier; and when a sxifticient nunibcr had been laid to bring tiie work up to 

 the height of low water spring tides, tlie whole heeadth was levelled, and all 

 the mie<iual projections chipped off, in order to prepare a bed for the firs 

 co\u-se of dressed masonry. The work then proceeded in the regular man- 

 ner, consisting of alternate headers and stretchers of properly squared ashlar 



Fig. 1. 



Hiifft 



^iT-J— «=n 



I'-l.r L ii- 



I 



JMiiiii-*iiiiii ' iiiiui - mil I 



4 Wutir 



in front, with dry stone hearting of squared scapple dressed rubble inside, 

 and in this way was carried up to the full height required. 



When the writer visited this work, in the year 1818, it had been advanced 

 a consideraole distance into the sea ; and although parts of it had been ex- 

 jiosed to some very hea^T storms, neither flaw nor settlement coidd he dis- 

 covered in any part of this excellent piece of dry-hnilt masonry. 



From an account of some foundations similar to that described above in the 

 recently published life of Mr. Telford, it may he seen that the practice has 

 been much more extensively adopted, and a far holder attempt carried out 

 by Mr. Gibb, of Aberdeen, than the one acted upon in the other work at 

 Ardrossan. The pier at Aberdeen is extended into the sea, with a bicadth 

 at the base of seventy-five feet, the bottom consisting entirely of irregularly 

 shaped masses of stone, which having been conveyed to the spot in boats, 

 were tumbled in by chance to the depth of ten or twelve feet. In the draw- 

 ings composing the Atlas, which accompanies the hfe of Mr Telford, the low 

 ^^■ater mark is shown about foiuteeu feet above the bottom, and in the narra- 



tive of this work by Mr. Gibb, he states, that the bottom under the founda- 

 tion is nothing better than loose saud and gravel, and that tlie front ashlar 

 commences at about one foot under low water mark, and is carried up to the 

 top of the iiier, which the drawing shows to be about thirty-three feet iu 

 height from the bottom to the top. The rise of the tide is shown to be 

 fourteen feet, the breadth of the pier twenty-eight feet, the sides carried up 

 with a slope inwards. Fig. 2, describes the method adopted by Mr. Gibb. 



Pier at Aberdekx 



^^?Si§>^:>Sj$§5;?i5Sss:S5^^~ 



The author next proceeds to describe an economical method of 

 building the foundations of a pier as practised by Mr. Telford at In- 

 verness, to avoid the expence of erecting a coffer dam. This is well 

 deserving of notice on account of its simplicity, particularly the part 

 explaining the " lewis." 



At the site fixed upon for the intended jiier, the depth of water, at the 

 lowest spring tides, was never less than foin- feet, and at ordinary low water 

 five or six feet; the bottom a very hard gravel, uuited with clay. The whole 

 length of the breast work was about one hundred and sixty feet, and through- 

 out this distance the bottom was dredged out, to the widtli of eight feet, and 

 depth of two feet, to receive the masonry. 



A simple system of piling was however driven previous to fouuthng the 

 masonry. The piling consisted of two bearing piles, twelve feet long, and 

 eight inches diameter, driven down at intervals of twenty feet ; and across 

 the heads of these piles, and level with low water mark, cross pieces of elm 

 planking twelve feet long three inches thick, .and one foot wide, were fasten- 

 ed xvith trenails. On the top of these were laid longitudinal half timbers, 

 one foot wide, and six inches deep, secured to the cross pieces and Ijcaiing 

 piles by rag bolts, driven into each pile head. 



The accompanying sketches, figs. 3 and 4, will amply illustrate the forms 

 and (Usposition of the timber work in the foundation. In addition to the 

 bearing piles, a row of timber slabs, of inferior quality, was also driven down 

 a few inches into the bottom, at intervals of about ten or twelve inches ; 

 these had a spike driven through them, near their heads, and into the longi- 

 tudinal logs of half timbers ; there were merely to answer the pmpose of 

 guide timbers, to set the stones by, and to determine the guage or breadth of 

 the work, and were afterwards removed. 



The bottom on which the pier was to be founded being now made as level 



Fig. 3. 



