HISTORY OF MARINE ARCHITECTURE

but the latter will be found much better adapted to encounter an heavy swell,than the former.

The imaginary lines into which the hull of a ship, in order either to give onearchitect a sufficient idea of the intention of another, or to enable the manualoperation to be carried on, in perfect obedience to the will of the contriver, aredivided into two parts or classes, perpendicular and horizontal. The first may besaid to describe the swell or form, intended to be given to the vessel, for the pur-pose of resisting the impulsive effects of the wind, constantly attempting to driveit to leeward, or out of its intended course, when going otherwise than directlybefore it. The second, mark the perfections of that form which is destined topass ahead through the fluid, or sea, with the greatest velocity, as experiencingthe smallest opposition.

In some instances, these considerations act in opposition to each other; andto this cause has been owing, not merely the difficulty ,ot ascertaining what arethe true points of perfection in each, but how far one principle can be made, orought to conform to, the other; that they may meet precisely at one point with-out any material counteraction. It will be necessary, on this occasion, to statecertain incontrovertible points, which may serve, not only as the basis of the presenttheoretical investigation, but, it is also humbly hoped, may save some labour tofuture students, by clearing before them, and pointing out the path, or paths,which they may, perhaps, find their advantage in pursuing, instead of wan-dering, almost without knowing the point of destination; or being able pre-cisely to describe, whither they themselves wish to go. The primary pointsfor the consideration of every marine architect, are two, and only two in num-ber, stability and flotation. The first means the power of resisting the wind,when adverse to the intended course ; the latter, that peculiar species of form,which enables the wind itself, or any artificial means used, in impelling a vesselto force it through the water at the greatest rate. From what has*been already saidon the subject of sliding keels, it must be evident these desiderata counteract eachother. A vessel, having a small draught of water, certainly passes, with thegreatest ease and expedition, before the wind ; while, in the other case, a pro-gressive immersion of the body, or hull, will be productive of advantage, inproportion to the extent of the principle.

Stability and flotation, by which latter term is meant swiftness, being the firstand principal points which strike the consideration of the naval architect, othertemporary or local considerations follow at an humble distance, prayingtheir wants to be attended in turn, as soon as the demands of their superiors

are