130 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[Mav, 



dock at Duke Shore l)elong:ina: to Messrs. Young, though standing 

 rel.itivelv very similar in position to their otlier docks, is stated hy 

 tlieni to he jieVhajis the most aivkward dock in tlie river, owing to 

 tlie flood tide from Limehouse Reach setting right into it; and they 

 consider that had its entrance heen mucli wider, or its direction 

 much more acute with the line of flood, much of this inconveni- 

 ence would have been avoided. 



Fi(j, 8. — Messrs. Dowson's Gra^•ing Dock at Limehouse is nearly 

 square to the stream; but from the" particular set of tide in this 

 portion of the reach, the flood making over from Cuckold's Point, 

 this dock points at a very obtuse angle towards the flood, as shown 

 upon the diagram; great diSiculty is consequently experienced in 

 docking a heavy ship, a considerable purchase being necessary to 

 keep her in position until near high water, by heaving down her 

 stern against the tide. The evil at this dock, and the one at Duke 

 Shore, is increased by the strength with which the flood tide sets 

 directly into them. , 



There is a considerable length of outer tidal basin, or entrance 

 to this dock, between the gates and the river; but as the quays, or 

 wing walls which form the sides are parallel to one another, and 

 in a line with the sides of the dock, it is obvious that no advan- 

 tage is gained in reference to the particular direction which a 

 vessel assumes whilst entering. This lengtli of entrance appears 

 likewise to have been principally induced from the particular 

 local position of the dock, a public street crossing it, and the site 

 of the swing bridge consequently determining the commencement 

 of the dock^ This latter remark likewise applies to the next exam- 

 ple, which is shown in the same illustration, being close adjoining, 

 and nearly parallel, to Messrs. Dowson's Dock, but pointing slightly 

 down the'stream, and consequently forming a more obtuse angle 

 with the flood than even the last example, and is, therefore, as 

 regards direction, even more awkwardly situated; but the widening 

 out of the wing walls forming the entrance, slightly increases the 

 facilities for vessels, both departing and entering, but the tonnage 

 of such vessels is inconsiderable. 



Fig. 9. — The Regent's Canal entrance lock, which leads into a 

 lai-ge basin, or wet "dock, admitting vessels of considerable burthen, 

 principally colliers and coasters, is nearly square to the stream; 

 but from the tide setting across, upon the flood, from the opposite 

 side, induced by the local formation of the river, tliough not in so 

 great a degree as in the last examples, this entrance forms in the 

 line of its direction an obtuse angle with the set of the flood. It 

 has a very bad character, on account of its direction and the small 

 distance between the wings at the entrance, which had no room 

 for expansion, from the gates being, as in graving docks, close to 

 the :-iver bank. The difficulty of docking a ship upon the flood, 

 must have been very great before the addition of the timber- 

 works, which, in effect, remo\'e the entrance gates further from the 

 run of tide, creating slack water in front of them, and, by giving 

 a greater width between the jaws of the entrance, allow somewhat 

 for the necessary obliquity in entering, and atiord more space for a 

 vessel's bow to be turned down whilst departing. 



Puj. 10.— Lavender Graving Dock, Rotherhithe, bears an excel- 

 lent character for its convenience for docking; it is nearly at right 

 angles, pointing slightly up the stream. But its character, as 

 must be evident from former examples, is not dependent upon its 

 direction, as from the particular set of tide away from it, in conse- 

 quence of the tide setting from the point below on tlie same side 

 to the opposite shore, it is left in an eddj', and consequently in 

 slack water. It becomes for these reasons nearly similar in its 

 conditions to a dry dock from a harbour, wet dock, or other still 

 water; it therefore cannot be taken as an example in point, except 

 so ftir as showing that there are particular localities and biglits 

 upon a tidal river where the direction of the entrance becomes of 

 less importance. Even there, however, from the gates being 

 placed so near to the river, the platform is carried beyond the 

 wharf-line, and the necessity for the extension of piers to form a 

 chandler has been involved. The object in this case, and with 

 ship-builders generally, has been, no doubt, in placing their gates 

 so dose to the river, to gel as great a depth of water as possible 

 with the least amount of excavation, and to shorten the dock as much 

 as possible, with reference to the expense of construction and the 

 cost of land. In many situations on the Thames the existence of 

 a road, or street parallel to and not far distant from the stream, 

 has been the cause of an encroachment upon the river. 



Fig. 11. — The Shadwell entrance of the London Docks points 

 so much down the river as to form a very obtuse angle with the 

 stream. The inconveniences that would otherwise result to vessels 

 entering arc, from various causes, obviated at this entrance, which, 

 in fact, bears a very good character. One of these causes is, that 



the set of the flood tide is across the river, towards the opposite 

 shore from the bight below tlie entrance, which is left in ctmipara- 

 tively slack water, and is thus more at right angles with the flood 

 on account of this particular set. The great width between the 

 wings and the additional timber external works also afford great 

 facilities, both when docking and undocking vessels. In this 

 latter case the capabilities arise, like those at the IJlackwall en- 

 trances of the AVest India Docks, from the judicious construction 

 of the external works, which, however, have in both instances 

 been, to a great extent, of subsequent formation, to obviate evils 

 attendant upon the original form. It will at once be seen, by re- 

 ferring to the plan of this entrance as it now exists, that the con- 

 veniences for docking must have been much less before the exter- 

 nal works were added. Tiie timber ])ier added to the western or 

 upper wing and the doljdiin, form, with the northern ])ortion of 

 the wing wall, a line of direction pointing up the stream, which is 

 the desirable direction for docking a ship upon the flood as she 

 swings round, her larboard quarter coming in contact with the 

 dolphin, and her starboard bow with the timber pier; she is thus 

 pre\'ented from tailing upon the shore on the upper side, as she 

 would otherwise have done without these external works. The 

 timber ])ier and dolphin on the lower side, perform the same ofjice 

 towards a vessel leaving the dock just after high-water, or being 

 docked, when there is no run of tide, and the south-west wind 

 blowing her on to the shore below the entrance. 



Much of the external wing wall on the lower, or eastern side, 

 might have been dispensed with, had the direction of its entrance 

 been more at right angles to the stream; it is, however, to be 

 observed, that this direction would not have suited so well as the 

 one adopted in the general plan of the docks. This entrance pos- 

 sesses an advantage pointed out in the instance of the Blackwall 

 West India Dock entrance, from the great width allowing two 

 vessels to pass. 



Mr. Henry R. Palmer, the engineer emploj'ed to construct this 

 entrance, published in 182S, a paper entitled "Report on the Pro- 

 posed Eastern Entrance to the London Docks." In that paper 

 Mr. Palmer says: — 



The taking of a ship into a harbour is required to be performed by the 

 persons on board, and therefore the line of direction of the entrance is made 

 as simple as her security from the wind and its consequences upon the water 

 will allow. If the same force can with safety be employeil to conduct a 

 vessel to stdl water which has taken her to the mouth of it, the entrance 

 will be performed with most ease. 



On the sea coast, the wind, and its consequences upon the water, constitute 

 the principal forces to be contended with; the current of the water being 

 comparatively of little or no value. On a river, the current of the water 

 becomes an essential force, and that in proportion as the width of the river 

 is diminished. 



It is obvious, that in both cases, it is preferable to make these forces sub- 

 servient to our purpose, when it is practicahle; and in the formation of an 

 entrance to a harbour, or a dock, its position, direction, and form, should he 

 such as to expose a vessel to as httle action as possible not available to this 

 object. 



The communication between a river and a wet dock, being through the 

 medium of a lock whose limits but little exceed the dimensions of the ship 

 that passes through, it is important that the water about the entrance to 

 that lock should be, if possible, quiescent. If it have a running or turbu- 

 lent motion, considerable labour is indispensably necessary to conduct a 

 vessel within its narrow channel with safety ; we therefore find that many 

 of the public docks are provided with an external area, or basin, which is lu 

 fact a harbour, whose entrance is sufficiently wide to admit vessels during 

 most weathers, while at tlie same time it has the effect of producing still 

 water where tlut is required. 



The adoption of this principle upon the Mersey and upon the 

 Humber, on account of the heavy sea, is referred to; also the 

 entrance to the Hull Docks, from the river Hull being formed in 

 a recess or fore-bay. 



The entrance to the Bristol Docks is referred to by Mr. 

 Palmer, as a precedent for the case then under his consideration, 

 where the entrance locks point down the stream and fcu-m an 

 obtuse angle witli the line of flood, and where, as Mr. Palmer 

 says. 



Vessels go up with the flood tide only, and sail most generally at once into 

 the entrance. When the wind is high and corresponds with tlie tide, a rope 

 is sent on shore op|insite the entr.ince, and being connected with the stern, 

 the ship is easily presented to the lock, and is conducted into still water 

 without risk. 



It may be observed, that the extreme narrowness of the Avon 

 necessarily induced such an arrangement. 



The particular position uf tlie entrances to the Runcorn Docks 

 is next reviewed; tliose through the locks, .Mr. Palmer describes 



