120 History of Mechanical Inventions and Useful Processes. 
vessel quickly, has been fitted up on board of a boat by Mr 
James Milne, under the inspection of Mr Fraser, the inventor, 
so as to be wrought by two men, who pulled at separate levers, 
in the same manner as the rowers pull at the oar. By means of 
two apertures, each of which was only one-fourth of an inch in 
diameter, the boat went at the rate of three miles an hour, though 
the machinery laboured under an imperfection, which has since 
been remedied. 
2. On the Substitution of Block-Tin Pipes in place of Copper 
ones, and on the Construction of' their Joints. By Mr 
James Milne, Brass-Founder, Edinburgh. 
In the month of June 1817, being then in London, I happen- 
ed to see a piece of copper-pipe, originally fths of an inch bore, 
which had been used for conveying coal-gas, so furred up, that the 
opening in the centre would scarcely admit a crow-quill ; and I 
was informed that several shops which had been lighted with coal- 
gas for eight or ten years were obliged to be refitted with new cop- 
per-pipes, the old ones being quite useless. These circumstances 
first induced me to think of substituting for that purpose pipes 
made of some other metal, which might obviate the objection to 
copper, of being subject to the corrosive influence of coal-gas. 
Pure block-tin occurred to me as a metal less liable to be act- 
ed upon than any other, possessing considerable ductility, and 
sufficiently strong when made of a proper thickness. Soon after 
my arrival at home, I tried to make a piece of block-tin pipe, 
cast upon a mandril, and drawn down to a proper thickness, 
say f th of an inch. In this trial I succeeded far beyond my ex- 
pectations, by turning out a pipe, not only nearly equal in ap- 
pearance to silver, but also capable of bearing a very great ex- 
ternal pressure without flattening. Previous, however, to intro- 
ducing this pipe to the public, about the close of the year 1817, 
I took to Glasgow a piece, of \ inch bore, and the usual thick- 
ness T ^th, in order to have it tried by a very powerful pump used 
at the gas-works there, for proving the pipes, to ascertain what 
pressure it would bear. Next day the sub-engineer returned it 
to me, saying he had applied to it the greatest power the ma- 
chine was capable of, equal to a column of water 1000 feet high, 
without being able to burst it, or even injure it in the smallest 
