HISTORY OF MARINE ARCHITECTURE:

bears more material reference to the improvement and perfection of the science,than any others that can be selected. It is not, therefore, with any intentionwhatever of depreciating the value of the enquiry, that any remark is made inrespect to its want of novelty, but merely for the honest and candid purposeof shewing, that theory, as well as philosophical investigation, were, evencenturies since, called up in aid, in support cf practical science, and that theancients by no means acted so much at random, on vague indeterminate opi-nion only, as the arrogance of modern refinement has, on some few occasions,rather too hastily promulged.

“ It follows, therefore,” proceeds our author, “ that the rudders, and theireffects, being influenced, in a very considerable degree, by the stream of fluidoccasioned in consequence of the swift passage made by the prow through it, thattheir most proper stations are at D, where they are empowered to act withthe utmost force, and not at B, where such force becomes considerably weak-ened, as standing in the eddy, created by the junction of the two artificialstreams,” Vossius takes this opportunity of explaining the cause why vesselsof great length answer or obey the helm better than such as are of more con-tracted dimensions, and assigns that reason as one of the principal causes whichdirected the minds of the ancients to the adoption of those principles in MarineArchitecture, which modem practice has since exploded. This opinion, however,appears rather too hastily formed ; for there can be but little doubt, that theaddition to the impulsive power acquired by such length, was the primarycause of it. It is remarked, with more truth, by the same ingenious antiquaryand commentator, that the dimensions of the rudders were affected, in a veryconsiderable degree, by the contour or shape of the bottom, as well as thegreater depth of water which some vessels drew in comparison with others ;or, to speak abstracted from scientific terms, that proportion of the hull, which,when the galley was at sea, sunk by its weight below the surface of it. Theuse of double rudders, a contrivance which, on some particular occasions, wasextended even to four *, grew into disuse, as the principles and views of navi-gation became enlarged, in consequence of the inconvenience which was foundexperimentally to result from it. It needs but little argument to prove, thatit must be much more difficult to produce a decided and precise effect fromthe operation of a machine, or engine, composed of two parts, than it wouldbe, provided that machine consisted of one only. This consideration and dis-

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