198 REPORT—1857. 
before the Section he was laying the grounds of meeting the British Association that 
day twenty years, and finding that the mode of mechanical construction which he 
proposed had been as universally adopted as the wave principle, because of the pub- 
lications of the British Association. 
The author then proceeded to give an elaborate description of the old method of 
constructing an iron ship, contrasting it with the improved style which he pursued 
at present. Instead of the mass of wooden rubbish, which did not strengthen the 
ship, and involved enormous expense, he placed inside the iron shell as many com- 
plete bulkheads as the owner permitted him to do, and then constructed in the in-. 
termediate spaces partial bulkheads, or bulkheads in the centre of which holes had 
been cut for the purposes of stowage. The deck was strengthened by introducing 
pieces of angle iron, and other contrivances; and as an iron ship when weak was 
not weak crossways, but lengthways, he strengthened it in this direction by means 
of two longitudinal bulkheads; and the result was a strength and solidity which 
could not be obtained in any other way. The ‘Great Eastern’ had all these improve- 
ments, and, in addition, the cellular system, so successfully applied in the Britannia 
Bridge, had been introduced all round the bottom and under the deck of the ship, 
giving the greatest amount of strength to resist crushing that could be procured. 
As he had already observed, there was nothing new in the ship but her great size 
and cellular construction. It was true she would be propelled both by screw and 
paddles, but there was no reason to doubt that they would work harmoniously. 
He wished he could tell them how fast she would go, but that was the secret 
of the owners of the ship. 
On the Importance of Regulating the Speed of Marine Engines. 
By T. Sirver. 
On the Formation of the Entrances to Tidal Basins. 
By Binvon B. Stoney, MRA. 
In the formation of the entrances to tidal basins, two points have to be considered : 
1. The shape of the entrance. 
2. Its position. 
In existing docks we find some entrances constructed at right angles to the river, 
others sloping upwards against the stream, and others again sloping downwards; 
which latter form not only tends to prevent deposits, but greatly facilitates the entrance 
and departure of vessels. Even though no downward current does exist in the river, 
that form of entrance which slopes in the direction of the vessel’s course presents 
obvious advantages, especially in the case of a narrow river, where it is essential that 
a ship should, both before entering and after leaving the basin, be in the line of the 
river, and at the same time not far from its centre, where the channel is deep and un- 
obstructed. 
The usual position of the entrance is at or near the centre of that side of the basin 
which is parallel to the river. This however is objectionable, since, besides promoting 
deposit, it makes it necessary that vessels lying within the basin be warped, at no 
small expense of time and labour, into a suitable position for passing through. al 
The chief considerations to be kept in view in the construction of floating docks or — 
tidal basins are as follows :— 
1. Facility of ingress and egress. 
2. Freedom from silting up. 
To these may be added,— 
3. Economy of quay room. 
4. Facilities for the land traffic in connexion with the dock. 
These conditions are, it is believed, in a great measure fulfilled by the form of en- 
trance advocated by theauthor. The general form of the basin is a lozenge, a trape- 
zium, ot a rectangle, whose width is equal to the breadth of two vessels together, with — 
sufficient space between them for another vessel to turn round freely: the entrance, 
placed at the lower end, is well sloped in the direction of the ebb current, and has its, 
