392 



THE CIVIL ENGINEER AND ARCIHTEcrS JOURNAL. 



[Decembeb, 



SHANNON IRON BRIDGE— GIGANTIC I'lLE DRIVING. 



A MOST important fact is recorded in connection with the pro- 

 trress of the Midland Great \\'estern Railway IJrid;;e over the 

 Shannon, in the sinking of cylinders of ID feet in diameter for the 

 foundations. This has been done with I'otts's pneumatic process 

 hy Messrs. I'"o.\ and Henderson, tlie contractors, who have likewise, 

 we believe, the working of the jiatent. We mentioned some time 

 ago that these cylinders were in i)ro(;ress of constrnctiun. and 

 looked forward with some interest to their application in jiractice. 



In reviewiii;,' Mr. Edwin Clark's work on the Britannia Bridfie, 

 we had the opportunity of describinfr the lar^re cylinders which are 

 beinf;^ put down liy .Mr'. I. K. Brunei, on the \\'ye, for that remark- 

 able structure which he is now carrying; out. The sinking? of those 

 cylinders as there described is not in the nature of ))ile-driving-, 

 and alth()U{;li tliey are of a very larj^e size, yet the 10 feet cast- 

 iron cylinders of Messrs. Fox and Henderson are the larpjest ever 

 applied in the nature of pile finnidatiuns, and on this account their 

 success is of material interest to our readers. 



The bridge is, we understand, of iron, and of large dimensions, 

 and is supported entirely on cast-iron cylinders, of the diameter 

 mentioned. The cylinders near the shore have been put down by 

 excavating and the application of weight; but those in the bed of 

 tlie river, l)y I'otts's process. We need scarcely inform our readers 

 t.iat, in this simple process, an air-pump is employed, which being 

 coiniccted with the liead of tlie hollow i)ile, tlie air is exhausted, 

 and a. stream of water, sand, shingle, and gravel, rushing up from 

 below, the pile sinks gradually into the disjilacement m;ide to any 

 required depth. It is therefore a kind of sub-aijuatic excavation, 

 the lower end of the hollow pile being converted into a kind of 

 scoop, worked by the air-pump on the platform above. The 

 exhaustion employed was 2Ci inches of mercury, ecpiivalent to 13 lb. 

 to the sipiare inch; and the cylinder was driven down between 

 .') and ti feet in a few minutes, or rather suddenly, until checked 

 by a piece of submerged or drifted wood. The operations were 

 under the direction of Mr. J. Millner, C.E., the contractor's 

 engineer; and the bridge abutments, which are of stone, under 

 Mr. Daigan, the eminent Irish contractor. The cylinders will be 

 filled-in with ('(Uiciete. 



Hitherto the piles employed for I'otts's process for sea-beacons, 

 for the Maeldraeth Viaduct, the Black I'otts Bridge, and other 

 structures, have been of very small diameter, so that the proce> d- 

 iugs we have just described are of the greatest importance. A 

 cylinder of 10 feet diameter gives a large bearing, and four such 

 cylinders will carry a large tablier or platform for a pier, and 

 which (^an be put down without cofferdams or other preparatory 

 works, thereby greatly reducing the expense of submarine founda- 

 tions. Here neither cofferdams, caissons, steam-engine pump, nor 

 diving-bells are wanted, only an air-pumj) of adequate power, 

 which can be easily carried about and rigged anywhere. It will be 

 obvious that unless sunk from the inside (when there would be as 

 much trouble for pumping as by the pneumatic process, and very 

 much labour and expeuditure of time), any external application of 

 jiower would, if it could be em|iloyed, exercise a very unfavour- 

 able effect on the material of the cylinder. Indeed, a force of 

 much less than l.'ilb. to tlie square inch would smash a hollow iron 

 cylinder to jiieces. Then again it is to be observed, that 10 feet 

 is by no means the limit of the diameter to which the cylinders can 

 be carried, so that it is open to engineers to design works in situa- 

 tions and under economical conditions where hitherto the resources 

 of art were insullicieiit to meet the emergency. 



IMPROVEMENTS AT GRANTON 



Most extensive impro\ements have been carrying on, for a con- 

 siderable time past, at tiranton harbour, says the .Scutunmii, and a 

 gratifying circumstance in relation to them lately took place. 

 This was the launch of an iron dredging-niachine for the deepen- 

 ing of the harbour, from the works of Messrs. S. and II. Morton, 

 who have only recently commenced business at Granton, although 

 w ell-known in connection with their extensive engineering estab- 

 lishment in Leitli Walk. 



The name given to the '"dredger" is appropriate — namely, "The 

 Ilowker."* It was designed by Mr. W alker of London, the cliief 

 engineer of the harbour, who was jiresent and took an active 

 share in the whole proceeding's. It is about 90 feel long, and '22 

 feet wide, with a depth of hold of about 9 feet. The engine with 



Jlowkcr is a bcotcti phrase for " digger." 



which it is to be fitted up will be about 20-horse power; and it is 

 calculated, we understand, that the dredger will work to the depth 

 of 20 feet from the surface of the water. It is expected to be 

 comjileted, and in full operation, in the course of a few weeks; 

 and the first work to which it will be set will be to make the inner 

 berth along the pier equal in de]>th to the outer one, which is 

 from 10 to 12 feet at low water of an ordinary spring tide. Al- 

 ready three barges have arrived at (iranton, to work in conjunc- 

 tion witli the howker. These are built of wood, and upon the 

 "hopper" principle, by wliicli they are enabled to discharge their 

 cargoes almost instantaneously in deep water. Two other barges, 

 made of iron, are to be built by the Messrs. Morton, and when 

 these are finislvd, Granton may with truth be said to have a 

 most thoroughly equipped drerlging establishment. 



Various improvements are going on at (Jranton of considerable 

 magnitude and importance; in addition to the noble pier that has 

 been completed some time, it is the intention of the noble pro- 

 jirietor, the Duke of Buccleuch, to erect a breakwater on the east 

 side of the pier and another on the nest, so as to inclose a spacious 

 harbour on each side. The area is about 77 imperial acres in 

 extent, and that of the eastern about 52. The breakwaters, like 

 two arms, will surround these harbours, with the exception of a 

 space of about 70 yards a little to the north of the point of the 

 pier, which is to serve as an entrance for the shipping. The break- 

 water on the western side, which is to be upwards of 1000 yards in 

 length, has been in progress of construction for a considerable 

 time, and is all finished except about a hundred yards. The 

 eastern breakwater has not yet been commenced, but arrangements 

 are under consideration for its being speedily undertaken. The 

 height of the western breakwater is about seven feet above high 

 water, so that, even as it at present stands, it will form a pretty 

 good protection for vessels in westerly and north-westerly winds; 

 but when it is surmounted, as it is designed to be, by a parapet 

 wall, the protection w ill be effectual from winds blowing from either 

 of these directions. In fact, when the eastern breakwater is 

 finished, as it is to be, in the same manner as the western one, 

 (iranton will almost be one of the safest places in the I^-ith of 

 Forth during a storm. These improvements will add very much 

 to the value of that rising port. 



It is his grace's purpose to lay down, without delay, a jiatent 

 slip, of great magnitude, for the benefit of all the large shipping 

 coming to this part of the country. This slip, which will be on 

 the principle of Morton's patent, will be the largest in the king- 

 dom, with the exce|)tion of one at Belfast. It will be sufficient to 

 allow vessels of 1000 or 1200 tons to be taken upon it for the pur- 

 pose of being repaired. 



THE AVATER SLT'I'LV OF LONDON. 



Report oil the Water Supphi nf London. By the Hon. M'im.iam 

 N.tPiER. — (Presented to the General Board of Health, (Jwyder 

 House, AVhitehall.) 



Part No. I. 



Farnham, Surrey, Oct. 2, 1800. 



My Lords and Gentlemen, — Having had the pleasure of receivinij in 

 August last your instructions to visit the gathcrina; grouids of tlie proposed 

 water supply to the metropolis, in order to gauge the streaius ami make a 

 eaiefiil re-e\atiiinjtion of the general capaliilities of the country for the pur- 

 pose intended, I have now llie honour to submit to your notice the results 

 of my observations, with a few remarks on the different bearings of the 

 scheme. 



On reading the Board's report presented to the Houses of P.irliaraemt 

 during the past session, I perceived that from the very short time at the dis- 

 posal of the Board the calculation of the qnaiilily of water available from 

 the rain-fall on the district, an extent of neatly lot) square miles, was neces- 

 sarily founded on the discharge of the streams at their outfall. 



The Board were thus also manifestly placed under great disadvantage 

 when endeavouring to ascertain the character of these waters ; for, as such 

 waters inevitably partake of the nature of the soils throngh wliieli they 

 have passed, and as the pure samls of the district are not only houiided hy 

 clay on the north-east, ea^t, and south-east, hy chalk on the west, hut are 

 also intersected from east to west in the south by a high rang.' of chalk 

 lulls, the course and outfall of these streams present crtaiiily a widely mis- 

 leading test of the quality of the water to he derived from pure sands. 



Considering the purity and softness of the supply to have tlie first claim 

 upon my attention, I remembered the principle enunciated hy the Board, 

 " the nearer the source the better the quality," and made it my first o' ject 

 to examine the nature of the soils in which the rain-fall of the country makes 

 its appearance after percolating through the upper crust, and ne.\t, the soiU 

 through which it passes to its uutl'all. 



