157 
Captain Hall’s Account of the Dundee Ferry . 
cut off at top, might be formed alternately of crooked timbers, 
made to cross over nearly to the opposite boat, so as to 
form an arch over the space between the two, extending the 
whole length of the boat (with the exception of the space occu- 
pied by the paddle-wheel in the middle). Thus this part, which 
is manifestly the weak point, would resemble a ship’s bottom in- 
verted. It might also be united firmly by sleepers or braces 
placed diagonally, according to Sir Robert Sepping’s plan, un- 
der or over the arch, and bolted firmly to the timbers. The 
beams would lie, as they do now, across the boats, and the deck 
over all, might be disposed across the length as at present, or per- 
haps in a still more binding manner, by being placed as the decks 
are in some of our line-of-battle ships, diagonally. In the Union 
twin-boat at Dundee, strong trussed beams are placed diagon- 
ally from the keelson of one division to the upper works of the 
other ; but it is found that these braces, which must pass 
through the water between the boats, impede her progress ma- 
terially. This objection would not exist, if, instead of thick 
trussed beams, eight or ten inches square, flat bars or plates of 
iron, shaped like the blade of an oar, were substituted. Four or 
five of these, if placed diagonally from the keelson of both divi« 
sions to the top of the external timbers of the opposite ones, 
would add immensely to the strength of the boat, while they 
would offer scarcely any sensible resistance to the water. It is 
confidently believed, that a vessel, so bound together, would not 
only encounter, without twisting, any sea likely to be met with 
in the Firth of Forth, but might be allowed to take the ground, 
to the full as safely as any other description of steam-vessel. In- 
genious practical men, whose attention was directed to strength 
and lightness would probably strike out many other contrivances 
for obtaining the end in view ; and when we see such long, and 
consequently weak, vessels, as the Soho and James Watt, en- 
countering heavy gales of wind and a high sea, without injury 
to their delicate machinery, we may safely conclude, that, when 
care is professedly taken to give strength to a twin-boat, there 
would be no twist sufficient to impede the true joint action of 
the two engines, which in practice is the material point to be 
gained. 
Supposing this point established, and twin-boats plying on 
