1839.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



169 



Wlien four reservoirs are attached to the look, as diagram fig. .1 

 shows, »e find the lift 



and therefore 





. The elevation of the hottom of the lowest 

 or the first reservoir above the lower level =^ R.r =: 



'2. The elevation of the bottom of the se- 

 cond reservoir above the lower level = i Rs = t- 



S. The elevation of the hottora of the 



third reservoir above the lower level := 3 Ri^ = 



4. The oKvation of the bottom of the 

 fourth reservoir above the lower level =: 4 Ra; =; 



5 The water saved is =4 R,r := 



L 



R + 1 



R. L 



-> R -f 1 



•2.R.L 



R + 1 



3. R. L 



6 R'+ 1 



i . R.L 

 .'. 11 + 1 



4 RL 



.5 R + 1 

 (R + l)-L 

 .3 R + 1" 



= ih 



6. The water used is = (R +1)* = 



7. The maximum of water saved is represented by 



4R. L 4oo I 4qOj 



5R-ff ~ 500+T ~ 5"ao 



Tins demonstration shows that b)' means of four reservoirs attached 

 to one lock, nearly four-fifths of the lockage-water that is wanted by a 

 common lock, may be saved. 



The annexed drawing, fig. 4, represents a cross-section of a lock of 

 fourteen feet lift, connected v/ith two reservoirs ; each reservoir to have 

 5,400 supeficial square feet area. It is immaterial how the bottom of the 

 reservoirs is formed, and it is necessary to liave it below the level of tlie 

 culverts, in order to prevent the dirt from being raised and carried into the 

 lock-cliamber. Tlie bottom of each reservoir should he at least one foot 

 below the mouth of the culvert, or lower, so tliat at least one foot of 

 water remains in each reservoir, after the reserved water is discharged. 

 The main object in constructing the culverts is, therefore, to have the 

 points N and O, or the higliest point in the bottom of the culverts so 

 fixed above th.e lower canal level, that their elevation answers the ex- 

 pressions given by the foregoing formula;. 



Fiir.4. 



The culverts in the lock-wall embankment are represented in the 

 drawing to be of wood. The culverts in the wall itself must be con- 

 structed either in the form of rectangular syphons, or straight linear 

 inclined, so that the mouth of the culvert of "the lower reservoir opens 

 into the lock-chamber, below the lower canal level ; and the culvert of 

 the upper reservoir enters the lock-chamber at an elevation equal to 

 '2R-.-, above tlie former culvert. The reservoirs may be formed either 

 by excavation or embankment, as the ground suits best. Where the 

 natural ground is pretty level and square to the centre line, and the 

 lock-walls are to be raised about one half their height above the natural 

 ground at th.e middle of the lock, it requires but very little excavation 

 aud embankment t® form the reservoirs. It often occurs that a depres- 

 ^ion in tlie ground, or a natural basin, near the lock, can be used to 

 great advantage as a reservoir, requiring nothing but a little more cul- 

 vert. Where there are two reservoirs, tlioy must be located either, 

 one on each side of the lock, or both on one side, as the ground suits 

 best. In the latter case, the two reservoirs must be separated by a 

 dam, either formed by excavation or embankment. The bottom of the 

 reservoirs, and their side slopes sliould be covered with coarse gravel 

 or slaty material, if such material can be had conveniently, in order to 

 keep the water more fresh and clean. 



The paddles are best placed in the upper parts of the culverts, as 

 represented in the drawing, in order to preverit a great pressure of the 

 water from the reservoirs towards the lock-chamber, and to keep the 

 water safely shut up. The paddles should fit very close, and move in 

 iron frames. 



Whenever the supply cf water is plentiful, the boats may pass the 

 locks without using the reservoirs for saving a little more time. How- 

 ever, the excess of time which is required'by using the reservoirs, is 

 very trifling, and the passage can be effected vvith far less inconvenience 

 and injury to the boats and locks, when the reservoirs are used, than 

 when not. The objections which any engineer has against high lift 

 locks, will be entirely removed by the construction of reservoirs. 

 Reservoir-locks will be found very useful on slack-water navigation, 

 where it is a great object to reduce the number of dams. If in such a 

 case the river bank on the side of the lock offers no favourable oppor- 

 tunity, and not sufficient room, witiiout removing great obstacles, as solid 

 rock, S;c. for the location of the reservoirs, the required width can ahvays 

 be obtained by shifting tlie lock a little more into the river, and by 

 omitting the lock embankment. A bridge built along the lock-wall 

 over the reservoir, will serve for a tow-path in this case. The attend- 

 ance of a reservoir-lock requires no more skill tiian a common lock, as 

 the state of water in the reservoirs aud the chamber regulates itself, 

 and the lock-keeper has nothing more to observe than to open the 

 paddles, and to shut them as soon as the water-level gets settled. 

 When the upper and lower levels are raised in time of a flood, the 

 water will then occupy a different state in the reservoirs, and the con- 

 templated saving of water will not he obtained exactly. In such a 

 case, however, to save water is no great object, and the reservoirs will 

 prove just as useful in all other respects. 



THE NELSON MONUMENT. 



Mr. Editor, — The unexpected decision of the Committee, to re- 

 open the competition, unfettered by premiums, not only awakens the 

 hope that now men who rank highest in the scale of art will deem it 

 a prize worthy of their practised arms, and enter the lists with an 

 earnest deiire to distinguish tliemselves as artists and as Englishmen, 

 but gives the public and the professions bre.".thing-time, so that the 

 soreness of the one, and the asperity of the other may be softened 

 down. 



I am quite old enough to recollect, that in the hey-day of exultation 

 after the victory of Waterloo, the House of Commons came to some- 

 thing like, if not exactly, a vote that a large sum of money shauld be 

 devoted to the erection of a public monument to commemorate it; 

 and I am quite certain that desings for Nelson and Wellington monu- 

 ments were advertised for in 1.S17. 1 know that designs were sent in, 

 that they were kept some weeks, that artists were then desired to take 

 them away, with an intimation that they might again be sent in, some 

 three months afterward : and I apprehend you will find, upon inquir}', 

 that the premiums were adjudged to Mr. Sniirke and Mr. Wilkins. 

 Why they were not executed your informant knoweth not, but mayhap 

 those gentlemen will favour the public (if what I state be fact) with a 

 view of them. If I mistake not, Mr. Flaxman proposed, as a fit monu- 

 ment, a colossal statue of Britannia, and published a pamphlet descrip- 

 tive of the design, and of the mode in which he would construct it. 

 These things are desirable to be known, and seen if it be practicable, 

 that the public may ascertain whether art has receded or progressed 

 since that day. Even did it no other service, it would caution critics 

 to be more sparing of their censure, when such a man as Flaxman 

 failed. Rut whether this can be done or not, in the absence of pro- 

 perly qualified persons, to undertake the task, will you allow one, who 

 may rank as something intermediate between an amateur and an artist, 

 and who has again and again, however feebly, considered the subject, 

 quietly to state the difliciilties wliich occur to him, that, if his opinions 

 be well founded, the competing artists may not be spirit-broken by 

 unfair and ignorant censure. I will first take the peculiarities wliich 

 attend this competition. The Committee have never stated what kind 

 of monument they think best fitted for the purpoce. Tliis alone is 

 sufiieient to paralyse the efforts of the most talented ; for who can 

 bring his mind etficiently to bear upon a subject which he is almost 

 absolutely certain is but a vfill-o'-wisp? Sculptor and architect, eacli 

 must fear that the sister art may be preferred, and consequently all 

 labour bestowed upon the other will be thrown away. In emphatic, 

 though common language, each feels that he is "working a dead 

 horse." I do in my heart believe that few of the Committee can tell 

 what they want, and am quite certain that not one of them can carry 

 out his own ideas, so as even to satisfy himself: how then can it be 

 expected that artists can remotely guess at what may perchance be 

 something likely to suit their fancy ? — Sooth to say, sir, I f>ar the 

 selection is vastly like that of a lady in a cap-shop. Another difficulty 

 is created by the situation which is pointed out for its erection. At 

 first view it seems exceedingly easy to design a monument to be set up 

 in Trafalgar-square; but we first have to consider what is to be done 

 with the ground, whicli falls from nortli to south some eleven feet at 

 one end, and only about four feet at the other : and next, how a space 



