he propellers in a small
pinnace, the propellers were shifted six or seven inches further out, and
with about ten per cent. less indicated horse power she obtained three
tenths of a knot more speed.

Mr. Barnaby asked Mr. Linnington whether, in designing twin screws for a
vessel of 8,000 i.h.p., he would make each screw, which would have to take
4,000 i.h.p., of the same diameter as a screw for a single ship of 4,000
i.h.p., of the same speed. Unfortunately in high speed vessels, from one
point of view, the faster they went for a given power the smaller the
diameter of the screw had to be, and the larger the pitch, so that in very
high speed twin screw vessels the ratio of pitch to diameter would be found
to come out very great indeed. In a twin screw torpedo boat, to be tried
shortly, they had a ratio as high as 1.64. In the case of the Inflexible it
was found, owing possibly to the position of the screw, that the whole of
the plates immediately over the screws were damaged. Mr. Beckett Hill had
been using, during the past three or four years, the twin screw steamers
the Ludgate Hill, Richmond Hill, and Tower Hill. These were all over 4,000
tons register, and indicated, when at work at full speed, 2,500 h.p. Before
he and his friends built these steamers, they built some very large tug
boats on the twin screw principle. At the present moment, four of the
fastest steamers building for the Atlantic service were to have twin
screws. The great obstacle to the extension of the twin screw in the
mercantile navy had been the fear that the projection of these screws would
make the vessels very difficult to handle, but he had found no such
difficulties. He had found it an advantage to put the point of the
propeller as near the deadwood as he could, without actually touching it,
and in the large steamers, as well as in the tugs, the distance was a few
inches. As to the point of safety, he thought it a great advantage to have
twin screws, and on two occasions twin screw vessels had met with accidents
which, but for the twin screws, would have necessitated their putting back
to New York for repairs. The Richmond Hill, on one occasion, met with an
accident to her machinery two days after leaving New York; but she was able
to come on with the second set of engines, and was only one day late in the
passage. No difficulty had been found in the docking and undocking of these
vessels, either in London or Liverpool, and while with single s