1849.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



133 



for an entrance; and I am of opinion, that all dock entrances should rather 

 incline upwards with the set of the tide, which would make them easier of 

 access upon tlie flood, as all vessels of any magnitude should be brought with 

 their head upon tide, to enter with safety where there is a strong current ; 

 but where an entrance is formed in an eddy or counter tide, which is to be 

 found in various parts of the Thames, I would recommend that the lock 

 should be placed at right angles with the flood, in the stream ; and when 

 there is a strong tide immediately across the entrance, it should incline up- 

 wards, with the lower pier-head carried about 25 feet or 30 feet further 

 into the stream, than the upper one, as that would cause a partial eddy, 

 and thereby make the entrance easier of access, as well as facilitate the 

 docking.' 



The great width of the Blackwall entrance of the West India Docks is ad- 

 vantageous as regards the undocking, as it admits of the inward vessel being 

 within the entrance, and leaves suflicient room for the outward ship to pass 

 out. In tliis respect the Shadwell entrance of the London Dock may possess 

 tlie like advantage." 



Mr. KiNippLE says : — "I have long paid attention to the diiTerent en- 

 trances into the various wet and dry docks on the banks of the river Thames, 

 and consider that an angle of 4.'j°, pointing up the stream to the set of the 

 tide, is ill every way the most eligible ; for instance, Limehouse Bridge 

 Dock, which I now superintend, from being nearly at right angles to the 

 stream, and from the set of the tide being so strong, particularly at the 

 height of the springs, when it is usual to dock large ships of heavy draft of 

 water, it is very difiicult to square the vessels and to place them in position, 

 without a large warp from their quarter, to heave on, with a great number 

 of men, assisted, within the last few years, by steam-power. This process 

 causes so much delay, that the vessel frequently cannot be hauled a-head 

 until nearly high-water, and then sometimes with only from three to six 

 inches water to spare. This, it will at once he seen, involves great risk — 

 indeed so much so, that I could name several ships that have grounded in 

 some dock entrances, and have overhung the sill of the gates from 20 feet 

 to 50 feet, owing entirely to the above causes. These difficulties would be 

 entirely obviated if the docks were excavated to the above-named angle, 

 because the pilot could keep the ship off in deep water, opposite the dock, 

 until fifteen or twenty minutes before high-water ; and when ordered to 

 bring her to (having every rope already prepared), he would he enabled to 

 make more certain of getting her safely in and secured than at present, 

 when so much labour and care are required. 



With regard to wet docks, I consider nearly the same angle to be equally 

 advantageous for bringing to and docking a large number of homeward- 

 bound ships, in one tide ; but with this difference — for undocking, the lower 

 pier-head would require to be carried out nearly at ligtit angles, projecting 

 about 40 feet or 50 feet, and rounded off; which would so widen the 

 entrance, that ships when being undocked, when they always come out head 

 first, may, provided they want to go down the river, that is to say, being 

 outward-bound, make a warp fast to the said pier-head, and with another 

 taken off to a buoy, laid out for the purpose at some convenient distance, 

 be enabled to swing with the tide, and at once proceed on their destination." 



Mr. Green says : — •' I have no hesitation in stating that the entrances of 

 dry and wet docks should point up, and not down the stream." 



Mr. Haslip says : — " My opinion is, that dry docks pointing up the 

 stream on the river Thames, at an angle of 45°, may answer every purpose. 



With respect to wet docks, I consider that they ought to be at right 

 angles, with a sufficient entrance. 



Respecting building slips, the angle or run is always governed by the 

 river wherein a new ship is about to be built and launched." 



Mr. WiGRAM says : — " I fear you will not arrive at any definite rule on 

 the subject; but it appears to me, that all dock entrances should point 

 upwards ; the degree will depend on whether the tide runs strong, or not, at 

 the point or part where the dock is to be constructed. You are of course 

 aware, that the set of the tide alters greatly in velocity at different parts of 

 the river; but, in my opinion, the stronger the set or run of the tide may 

 be across the dock entrance, so much more should it point up, for the con- 

 venience of using the dock." 



Mr. Redman begged to acknowledge, and to offer his thanks for 

 the assistance afforded him by the proprietors of docks and the 

 officers of dock companies on the river, and he requested it might 

 be understood, that when he had designated a dock entrance as 

 "bad," or "indifferent," it was not meant invidiously, but that 

 from circumstances, or locality, it was not so favourably situated 

 as others which he had especially denominated as "good." 



He then referred to the drawing of the Blackwall entrance of 

 the West India Docks (fig. 2), and stated, that there vessels could 

 not be brought in so readily as had been originally intended; but 

 they were brought up head upon tide, and were warped in; also to 

 the Shadwell, or lower entrance of the London Docks, (fig. U), 

 which although pointing down the river, and forming an obtuse 

 angle witli the line of direction of the flood, was yet, by the addi- 

 tional works at the entrance, resolved into a very advantageous 

 form; for the upper wing, with the timber jetty and dolphin, 

 formed a rather acute angle with the particular set of the flood, 

 and was therefore advantageous for docking vessels; the lower 

 works formed at the same time a good direction for vessels depart- 



ing, and being brought up head upon tide. Viewing the particular 

 outline of the London Docks, it was obvious that a direction 

 pointing up the stream would have entailed so bad an angle of 

 communication with the docks, and so awkward a turn for the 

 vessels, as to render such a position next to impossible. 



Fig. 14. was a plan of the St. Katharine Dock's entrance, where 

 the direction, as liad been before explained, was rendered of less 

 importance by the great depth of water, which allowed vessels to 

 be docked after high water. At such a site as tliis, a wide 

 entrance was almost unattainable, from the great value of the 

 land. 



Figs. 15 and 16 were drawings of what appeared from evidence 

 to be good forms for entrances: the former for a graving dock, at 

 an angle of 45°, with a projecting pier on the lower side ; and the 

 latter for wet docks, at an angle of 60°, — the upper wing turning 

 at an angle of 45° upwards, and the lower at a similar angle down- 

 wards, together with a projecting pier. Such an entrance would 

 afford equal facilities for docking and also for undocking; a 

 double lock was also shown. 



There was another question, which however had not been 

 touched upon in the paper — viz., the best angle for a wall along 

 which a vessel would pass to enter a lock : for instance, upon a 

 canal, what angle would give the least amount of resistance to a 

 boat entering a lock? This, however, was not of importance in 

 reference to the present in<[uiry; still it was an interesting ques- 

 tion, well deserving the attention of the Institution. To illus- 

 trate the notice as to docking vessels, he might remark, that iit 

 Messrs. Young's establishment at Limehouse, where a large go- 

 vernment steam frigate was now being fitted, it was found neces- 

 sary, in docking that vessel, to connect a warp from her starboard 

 quarter to a capstan at the West India Dock in order to keep her 

 in position, on account of her great length. 



Remarks made at the Meeting after the Reading of the foregoing Paper. 



Mr. AValker praised the talent and industry displayed by Mr. 

 Redman, in collecting the examples shown by the drawings; the 

 majority were matters of fact, and the compiled drawings (figs. 15 

 and 16) were theoretical examples, deduced from reasoning upon 

 the facts now laid before the meeting. It must be borne in mind, 

 that from the value of land in the vicinity of London, and more 

 particularly of river frontage upon the Thames, the direction of 

 the entrances must have been, to a great extent, legulated by local 

 circumstances. For instance, the Shadwell entrance to the London 

 Docks could not have been differently placed, because, from the 

 jiosition of the docks, any other than a direct entrance would have 

 created greater inconvenience tlian any facility of entering could 

 have compensated for. At the same time, from a local eddy, there 

 was slack water in front of the entrance. 



The entrances to private docks were even more governed by 

 locality, and the influence that might be exercised upon the neigh- 

 bouring property; because in the case of an oblique entrance, the 

 vessels in entering or leaving the dock, would traverse and occupy 

 the frontage on either side of it. There was no doubt of the theo- 

 retical correctness of making the entrance to point obliquely up 

 the stream, if it was situated in the run of the tide, and the 

 locality permitted it; but where there was not any run of tide, 

 or an eddy existed, or where a deep fore-bay could be formed, 

 the entrance might he quite as advantageously placed at riglit 

 angles with the stream. It must, however, be considered, that in 

 entering, wlien a vessel came up with the tide, it made fast, and 

 then swung. In the case of the right-angle entrance, the tide 

 striking upon the broadside would have a tendency to drive it up- 

 wards; wliereas the tide striking a vessel obliquely, would have less 

 power upon it, and less force would be required to draw it across 

 the tide into the dock. When the mouth was widened, and was 

 shaped as in fig. 16, the current would assist a vessel, and with a 

 judicious arrangement of buoys, vessels would be docked very 

 rapidly; and in such cases, if the locality permitted, the angle 

 pointiiig upwards was advantageous; but where still water existed, 

 from a bend in the river, or the tide was sluggish, a rectangular 

 entrance would be found as useful, and in general would accom- 

 modate itself better to the property upon which the dock was 

 situated. 



Mr. Rennie thought the author had taken very judicious views 

 of the subject; it was, however, evident that engineers must be 

 governed by local considerations, and the velocity of the tide. 

 The late Mr. Rennie had designed several entrances pointing up 

 the stream, and with the widened mouth like tig. 16; but in prac- 

 tice, it had been found necessary to adapt them to the locality, and 

 with reference to the adjoining properties. Mr. Rennie had ar- 



