A.—­That will depend very much upon the locality where the comparison is made.  In the case of vessels performing distant ocean voyages, in which they may reckon upon the aid of uniform and constant winds, such as the trade winds or the monsoon, sailing ships of large size will be able to carry more cheaply than any other species of vessel.  But where the winds are irregular and there is not much sea room, or for such circumstances as exist in the Channel or Mediterranean trades, screw vessels with auxiliary power will constitute the cheapest instrument of conveyance.

612. Q.—­Are there any facts recorded illustrative of the accuracy of this conclusion?

A.—­A full paddle vessel of 1000 tons burden and 350 horses power, will carry about 400 tons of cargo, besides coal for a voyage of 500 miles, and the expense of such a voyage, including wear and tear, depreciation, &c., will be about 190_l_.  The duration of the voyage will be about 45-1/2 hours.  A screw vessel of 400 tons burden and 100 horses power, will carry the same amount of cargo, besides her coals, on the same voyage, and the expense of the voyage, including wear and tear, depreciation, &c., will be not much more than 60_l_.  An auxiliary screw vessel, therefore, can carry merchandise at one third of the cost of a full-powered paddle vessel.  By similar comparisons made between the expense of conveying merchandise in auxiliary screw steamers and sailing ships on coasting voyages, it appears that the cost in screw steamers is about one third less than in the sailing ships; the greater expedition of the screw steamers much more than compensating for the expense which the maintenance of the machinery involves.

SCREW AND PADDLES COMBINED.

613. Q.—­Would not a screw combined with paddles act in a similarly advantageous way as a screw or paddles when aided by the wind?

A.—­If in any given paddle vessel a supplementary screw be added to increase her power and speed, the screw will act in a more beneficial manner than if it had the whole vessel to propel itself, and for a like reason the paddles will act in a more beneficial manner.  There will be less slip both upon the paddles and upon the screw than if either had been employed alone; but the same object would be attained by giving the vessel larger paddles or a larger screw.

614. Q.—­Have any vessels been constructed with combined screw and paddles?

A.—­Not any that I know of, except the great vessel built under the direction of Mr. Brunel.  The Bee many years since was fitted with both screw and paddles, but this was for the purpose of ascertaining the relative efficiency of the two modes of propulsion, and not for the purpose of using both together.

615. Q.—­What would be the best means of accelerating the speed of a paddle vessel by the introduction of a supplementary screw?