Mr Robison on the Malleable Iron Passage-Boat^ 
masses or icebergs, found afloat in such abundance in the sea to 
the westward of Greenland. Thus, the extent of surface occu- 
pied by each iceberg, is limited by the mountains on three sides, 
and by the sea, in a measure, on the fourth ; but as to its thick- 
ness, there seems no natural obstacle to its perpetual increase. 
Art. III. — Account of the Malleable Iron Passage-Boat, now 
plying on the Forth ami Clyde Canal. In a Letter from 
John Robison, Esq. F. R. S. E. to Dr Brewster. 
Dear Sir, The Grove, December 1819. 
I HAVE now the pleasure of sending you the memoranda 
and sketches you wished for, of the malleable iron passage- 
vessel, constructed last winter and spring for the service of the 
Forth and Clyde Canal Company, by Mr Wilson, ship-build- 
er, from the designs, and under the direction of a very able en- 
gineer, Mr Henry Creighton, late of Soho, and now of Glasgow. 
The Hull was built of iron, in order to avoid the often 
recurring and expensive repairs to which the wooden vessels 
had been found liable. Considerable opposition to the plan 
was made by the persons connected with the navigation of 
the boats, who said it would be found inconvenient and unfit 
for the service ; but experience has proved it otherwise, and 
The Vulcan has been found to be the most agreeable and 
manageable of the passage-vessels in every variety of weather, 
while, though carrying more passengers than any on the old 
plan, it is as easily tracked as the smallest of them ; and from 
the lowness of the centre of gravity, it admits of a large cabin 
and awning on deck, where the passengers are better accommo- 
dated than in the former way below. The dimensions are. 
Extreme lengtii, - - - - 63 feet. 
Beam, ------- 13 
Depth, (including 5 inches keel) 5 
, , Abaft. Forward. 
Draft of water of the iron hull, when 
launched, - -- -- -- - 22 inches, 19 inches. 
Ditto, when fitted up with cabins, 
&c., - - 37 2^ 
Ditto, with 200 passengers and 
their luggage, - under 48 on an even keel 
