1845. 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



321 



bottom of the lock-pit had risen to a greater height than the sides, exhiliit- 

 ing on its surface, peat moss, roots of trees, and a great variety i>f marine 

 plants, rushes, fern, &c., but with very little water. It was, however, now 

 evident that there would he much water to contend with in sinking to the 

 required depth for the foundation. In order to accomplish this, a complete 

 close kirbing of whole timber piles was driven, enclosing a space for the in- 

 vert and the side walls of the lock ; these piles were well strulted by trans- 

 verse whole timbers. The excavation was then made, and the lock was 

 founded in short lengths between the transverse struts. It was presumed 

 that the pressure of viater from the tide without the lock would have a ten- 

 dency to force up and raise the invert and the gate platform ; several flues, 

 formid of elm plank trunking, were therefore laid in the rubble masonry, 

 which formed the bed for tlie invert ; these flues were carried under and 

 throughout the lock, and terminated in a vertical well, beyond the upper 

 gates of the lock ; thus the suli-water was allowed to circulate, and to rise, 

 without obstruction, to a corresponding height with the tide. This had the 

 desired effect, for the platforms never exhibited any tendency to rise, and 

 there was no settlement in the masonry. 



Mr. Telford, who saw this work in progress, declared he had never seen 

 so troublesome a foundation, and he highly approved of the method adopted 

 for preventing the upward pressure of the snb-watcr. 



Ciicumstances occurred of a very similar charac ter in forming the canal 

 from the lock, upwaids, across the mud-lands in the tideway. This was ac- 

 complished hv excavating the bed of the canal, through the mud, which was 

 tolerably sliffl and embaii^king the sides. When tlie tide was once excluded, 

 there was very little trouble with the water in the cutting; t'le work stood 

 well for some months, and did not subside to any remaikable extent; but 

 suddenlv the substratum, in several places, rose up i.i the bed of the canal, 

 to the height of 9 feet or 10 feet, exhibiting peat .and vegetable deposit, 

 similar to that found in the lock-pit, and the banks, on the siiles, sunk per- 

 pendicularly to a depth equivalent to the rising of the boltum. In these 

 places strong piles were closely driven in the lines of the bottom of the canal. 

 These piles were supported by transverse inverted arches of rough stone, 

 about C feet in width, and were laid about 20 feet apart ; when these were 

 finished, the excavations were re-made, and the banks were reformed ; after 

 which the work stood well. 



Ol/servalions. 



Sir John Rennie, President, said, he believed there was little doubt of 

 the Exeter canal being the earliest canal upon which true pound-locks 

 bad been constructed in this country, and that the Sankey cut was next in 

 date. There was much obscurity as to the first use of locks on continental 

 canals ; their introduction had been attributed to Leonardo da Vinci, but 

 there were reasons for believing they had been used earlier in Holland and 

 in China, which was rendered probable by the great attention paid to by. 

 draulic architecture in those countries. 



The ancient method of navigating rivets, was by waiting for the flashes of 

 land-water, when whole fleets of boats were carried simultaneously over the 

 shoals ; then came single gates for pounding the water, and producing the 

 same effect by artificial means; at length the true locks, in side cuttings, 

 were introduced ; and at present there were many specimens, not only of 

 very perfect river and canal locks, but also of immense locks leading to docks. 

 One of very extraordinary dimensions had been recently proposed, by Mr. H. 

 Martin, for the East India Docks. The design was for a lock 300 feet long, 

 and 75 feet in breadth, with its cills, 16 feet below low water mark. 



Oblique JVeirs. 

 Mr. CuBiTT, V.P., objected to the construction of locks on the direct course 

 of a river, for many obvious reasons, which, however, he would not then enter 

 upon, as be would do so fully in an account of the works upon the river 

 Severn, which he would request Mr. Williams, the resident engineer, to draw 

 up for the Institution. When he undertook the improvement of the river 

 Stour, in Essex, he found a very primitive system of navigation. There were 

 13 locks, and there were also 13 •' stanches" along the course of the river, in 

 the middle of the stream, without any side cuts. As few, if atiy, " stanches" 

 now existed, he would explain their construction. Two substantial posts, 

 with a bottom cross cill, were fixed at a given distance apart, sufficient to 

 permit a boat to pass easily between them. Upon one of these jiosts was a 

 beam turning on its centre, and long enough to span the opening. When 

 the stanch was used, the boatmen turned the beam across the 0]iening, and 

 placed vertically in the stream a number of narrow planks resting against the 

 bottom cill and the swinging beam, thus forming a weir, which raised the 

 water in the stream about 5 feet high ; the boards were then rapidly with- 

 drawn, the swinging beam was turned back, and all the boats which had 

 been collected above were carried by the flash over the shallows below. By 

 repeating this operation at given intervals, the boats were enabled to proceed 

 a distance of about 23 miles in two or three days. This system was, at one 

 period, very common in England. Then succeeded the pound-lock, contain- 

 ing sometimes twenty boats. The necessity of rapid conveyance had 

 induced gradual improvements, until the locks, as now constructed, appeared 

 to be almost as perfect as they could be made. The method of filling and 

 emptying tbi tn from culverts, with several latrral openings, was practically 

 very advantageous. Tb's system had been adopted in the locks in the Severn ; 

 hut the principal novelty in those works were the oblique weirs, relative to 

 which there had been so much discussion before the I'arliamentary Com- 

 niittee on the Bill. 



The object of those weirs vras to raise the water, and to retain it at a pro- 

 per height, for the navigation of the shallow parts of the river, without op- 

 posing such harriers as should prevent the free discharge of the flood waters. 

 Tliis end had been completely answered ; there was now a depth of upwards 

 of G feet of water at all times, where formerly there was only a depth of 18 

 inches, and during floods the back water did not rise higher than before the 

 establishment of the weirs. A similar result might, he believed, be always 

 attained, by making the obliquity of the weir sufficiently great; a regular 

 sheet of water would constantly flow over it, and its capacity would enable it 

 to discharge any increase with facility. 



Mr. R. Stephenson had seen the Severn improvements, and had been 

 much pleased with their apparent success. The sulijcct was of great interest 

 to engineers, as it involved a sieming paradox, that the placing an enlarged 

 obstacle across the bed of a stream, should not increase the height of the 

 (lijods above it. Such, however, was the case, and be could only attribute this 

 result to a diminution of friction, arising from the retention of a certain depth 

 of water over shoals ; the flood waters, as they came down, were no longer 

 retarded by the friction of a number of obstacles, but they flowed readily and 

 more rapidly along, until they reached the weir, where (rom its greattr capa- 

 city arisitrg from its oblique position, the body of water was more easily dis- 

 charged. In fact, the reduction of friction enabled a greater quantity of 

 water to pass along the channel in a given time. 



Mr. CuDiTT, V.I'., agreed with Mr. Stephenson's views. The oblique weirs 

 would raise the water to a certain height, above which it could not rise in a 

 greater degree than heretofore. It had not been assumed that this effect 

 would be to reduce the onlinary height of floods, but that they would pre- 

 vent the sudden effect of floods upon the adjoining lands. It should be stated 

 at the same time, that the channel of the river had been improved in several 

 parts, and the capacity of the stream bad been slightly increased, by the 

 works which had been executed. The practical result of these works had 

 proved, that an oblique weir, placed in a narrow channel, offered no greater 

 resistance than did its cross section by a line at right angles to the course of 

 the stream. 



Sir John Rennie, President, thought that the natural consequence of the 

 improvements in the channel was to gain a greater capacity for getting rid 

 of the flood waters. 



COMPETITION DESIGNS. 



Sir — Some four months since I forwarded a set of drawings which 1 had 

 prepared as a Design for a New Church to be built at Camden Town. The 

 instructions of the committee were sufficiently clear and decided, indeed 

 rather unusually so, and in them the amount to be expended was strictly 

 charged as not to exceed ij6,000. These instructions I kept in constant 

 consideration, anxious to do all that was possible for the £6,000 — and no 

 more; and of course relying on the honest juilgment of the Committee, and 

 a spirit of honourable and generous competition amongst my professional 

 brethren. 



The Committee had (with much judgment as I /hen thought), limited the 

 competition to a certain privileged number of architects, and in truth 

 every prospect was afforded of a fair and just decision. 



After the prize drawing had been named, the others were exhibited, and I 

 paid a visit to satisfy myself as to the justice of the selection. -Now, I own 

 myself beaten ; there were, I was going to say, half-a-dozen designs that even 

 in my partial judgment excelled mine. But how was it .' 1 knew that they 

 could not be executed for the money ; indeed one of them did not profess it. 

 for the estimate was £6060, and yet it was allowed to remaiii in competition, 

 and to my knowledge was voted for as the design which aught to be ac- 

 cepted ! 



The design which was chosen, it has since been discovered would, if 

 executed, much exceed the prescribed amount. In this dilemma, the Com- 

 mittee have desired the architect to make a new design which wilt come 

 within that sum — never dreaming of the justice due to those gentlemen who 

 expended their time and skill in their production of the other designs, and 

 which it is fair to infer were rejected, because they were honestly prepared ! 

 Out upon it! say I — and let us have no more to do with competitions, 

 whether they be open or limited. As well — and with more justice — might 

 you set Broriie, Lawrence and Suthrie, in competition upon a dead subject, 

 in orrier to discover who was best fitted to practice on the living one. But 

 which of the three would submit to the ordeal ? So long as Committees for- 

 get that they are as bodies by the same rules of honour and honesty which 

 maik their inrfi»/rf«o/ course, so long will architectural competition be no- 

 thing better than a delusion and a fraud. To this I would add that so long 

 as there are those in the profession who will take a mean, dishonest, and un- 

 gciitlemanly advantage of their brethren, by submitting false estimates of 

 their works, so long will the more worthy of their number be precluded 

 from joining issue. 



I am. Sir, your very humble servant, 



C. W. T. 



Portsmouth, Auijxist 19, 1815. 



