Mr. White said that as soon as it was found that with twin screws they lost
nothing in efficiency, ship owners generally were contemplating their
adoption, an admirable example of which had been set in the vessels of the
Hill line. In adopting twin screws, the question whether they should
overlap was one that deserved very serious consideration, and it was
interesting to know, from experience gained by the vessels of the Hill
line, that there was no difficulty in the way of the projection of the
screws. With a moderate power, and with vessels of considerable size, the
screws were well sheltered: but in the large ships which were contemplated,
where there must necessarily be larger screws, this might be different, and
become a difficulty.

Mr. Linnington, in reply, said there was no reason to think that the twin
screw at sea might not be as satisfactory, in comparison with the single
screw, as it appeared in smooth water. As a matter of fact, one of the
great advantages of twin screws was that at sea the condition of weather
which would bring the single screw out of the water, and make it extremely
inefficient, would have no appreciable effect on the twin screws. In
vessels of deep draught especially, they were well immersed, and they were
really more efficient at sea than in smooth water. In ships of full form,
the longitudinal position of the screws was of importance; but in the ships
referred to in this table the run was very fine, and the screws were well
covered by the hull. He did not think, in such a case, any small difference
in longitudinal position would affect the performance. If any alteration
were made, it would probably be better to put the screws farther off. When
the rudder was hard over, the blades of the screw should be about a foot
clear of the rudder.--_Industries_.

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