132 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



Ma^ 



should swing with her bow downwards. Ships are frequently taken 

 out witli their sails set on a fair wind, and in such a case, a fault 

 in direction would be still more severely felt. 



A direction nearly scjuare to the stream is recommended by 

 some authorities as tlie best for wet docks; others recommend an 

 acute aof^le of about ()0° with the flood, as shown in fi^. IG. The 

 amount of this aiifile, however, becomes of less importance if a 

 jjreat widtli is ol)tained at the entrance, by rounding out or splay- 

 iujx tlie wings. The upper win;;, or pier-head, should be formed to 

 a flat curve, or even a straifjht line, so as to present a favourable 

 angle to the tide for a ship entering. The lower pier-head, or 

 wings, should be rounded, or splayed off very much, I admit of 

 a vessel, whilst going out, turning with her head upon tide; it 

 should also project about 30 or 4-0 ifeet further out tlian the upper 

 pier, in order to cover the entrance and render it more accessible. 



The great variations that exist in the examples on the Thames, 

 are attributed by persons interested in shipping, to the importance 

 of the subject never having been sufficiently considered, and also 

 to want of capital and available space on the banks of the river. 

 The positions of dry docks have, no doubt, in many cases been 

 regulated, irrespective of any other considerations, simply by the 

 particular arrangement of the ground in which tliey have been 

 constructed, the direction of the first dock regulating that of its 

 successors, which were built parallel to it. 



The great desideratum with docks of each description appears 

 to be to obtain as great a width as possible at the immediate 

 entrance, and the larger this is, of less importance does the angle 

 become. The width is considered by many shipwrights as the 

 most important element of consideration; with a great width, a 

 small amount of heaving on one purchase or the other will correct 

 a great amount of error in direction. A ship, when being docked 

 at such an entrance, first touches the upper pier, and her stern 

 must then be drawn down, to bring her in a line with the entrance; 

 the greater the width therefore the better angle for leverage, or 

 purchase, will be obtained. It is also a great desideratum toafl'ord 

 plenty of room to pilots, whether they happen to be taking vessels 

 into or out of wet docks. 



As regards building slips; their direction appears, like many 

 instances of graving docks, to have been influenced, on the banks 

 of the Thames, and perhaps also on other rivers, by internal local 

 circumstances connected with the tenure and di\ision of proper- 

 ties; the construction of one slip has also governed the direction 

 of those in the immediate vicinity, which are generally parallel to 

 the first. This direction, it will at once be seen, cainiot be so im- 

 portant as in the instance of graving docks; still, however, as 

 vessels are launched stern foremost, and usually about the same 

 period that admittance into graving docks takes place, the same 

 reasons that influence the direction of one would aft'ect also that of 

 the other: that is, a vessel being launched, and her stern carried 

 up, her head would be brought up against tide, which is the most 

 convenient position for mooring her — conseqiiently, a position 

 slightly inclining up the stream, appears desirable; practically, a 

 direction square to the stream, answers the purpose, and is the best, 

 having reference to the value of a river frontage. 



The directions herein referred to as apparently the most desira- 

 ble, are — an angle of about 45° pointing u|> the stream, for Graving 

 Docks; an angle of ab(Uit <H)°, in a similar direction, for Wet 

 Docks; and a right angle for Building Slips. 



No one knows better the importance of the subject than the 

 shipwrights and pilots, and with how much less risk vessels may be 

 docked at some establishments than at others. The operation of 

 docking a valuable ship, with perhaps but very few inches to 

 spare, is at all times a nervous process, and they who are in the 

 constant habit of conducting such operations can give the best 

 practical opinions on the subject. 



The opinions of Mr. Dowson, Mr. Knight, Capt. Bond, Capt. 

 Evans, Mr. Kinipple, Mr. Green, Mr. Haslip, and Mr. Wigram are 

 given in letters to Mr. Redman, from whence the following extracts 

 are made: — 



Mr. DowsON says: — " I have read with some attention your remarks on 

 the several wet and dry dock entrances on the river Thames, and also ex- 

 amined the sketch you sent me (fig. 16). 



I feel a strong conviction that a great error has been committed in the 

 construction of most of them. My opinion is, that the entrance should 

 stand in a line, nearly up and down the stream; so that when a ship comes 

 alongside the jetty, for the purpose of docking, the bow would easily enter, 

 and much time and labour be saved in heaving the stern down against the 

 flood tide. 



The entrance into my dock and Duke shore are both very bad, and tLe 

 evil is increased by the llaod tide running particularly strong. 



I admit that, in wet docks, where the entrances, or jaws outside the dock 

 gates, are generally so wide, the evil is not so severely felt ; hut I remember 

 when the West India Docks, Ulackwall end, were first made, the danger for 

 loaded ships was so great, that it was found necessary to extend the upper 

 pier in the manner I prefer. 



I attriliute the bad entrances to want of judgment, want of capital, and 

 perhaps of space on the shore of the Thames." 



Fig. I*). — Proposed Wet Dock. 



Scale to Figs. 15 and 16, 1 Inch to 100 Feet. 



Mr. Knight says : — "With reference to the general question, F think it 

 may be presumed, that the entrances to the public dock establishments have 

 been constructed in a manner deemed most eligible (having reference to the 

 set of the tide), for the purpose of docking loaded ships, and that the con- 

 struction of the graving docks has been more particularly determined by in- 

 ternal considerations, as regards the ground on which the docks have been 

 formed, although the entrances to the public docks may, in some cases, have 

 also been influenced by similar considerations. As regards graving docks, it 

 is to be observed, that they are comparatively but seldom used, and that the 

 slack of tide is generally taken advantage of to dock the vessels. 



The entrance to the East India Docks, pointing upwards to the stream of 

 tide, is probably the best direction which could be given to it, as the stream 

 of tide runs rather strongly across it, and until the introduction of steam- 

 tugs, large vessels would occasionally hang until the tide slacked; now 

 by means of a quarter rope, the stern can be hove down the stream, when 

 the head is ponited to the lock, and the vessel bri>ught into the line of 

 direction of the lock without the vessel being brought to a right angle with 

 the stream. 



The following are the observations I have received from Captain Bond of 

 the East India Docks, and Captain Evans, of the West India Docks. 



Captain Bond says: — ' I think the East India Dock entrance has an ad- 

 vantage over the other docks, in having plenty of room in the river, and the 

 tide never running hard, except when it blows with an easterly galej and 

 now we have the use of the tug to keep the ship's stern down, we can dock 

 immediately we have water; before we had tugs, if the wind blew hard, the 

 large ships would hang until the tide slacked.' 



Captain Evans says : — ' 1 am decidedly of opinion that the Blackwall 

 entrance into the West India Dock is by far the best constructed in the port 

 of London, its bell mouth giving sufficient room to kant the l.irgest vessel 

 that ever was docked in the port, and that without the assistance of cither 

 a qnarter-rope or that of a steamboat; although it must he admitted that 

 the length of the lock is in some measure an impediment to the quick dis. 

 patch of business. Had the basin been carried aliout 70 feet further out, and 

 the bridge kept within the lock-gates, I should then consider it a perfect model 



