Water lines at various angles of inclination are then drawn on the body plan, all intersecting the water line for the upright condition at the centre line of ship. The displacement represented by the inclined water lines thus drawn, generally not being equal to that for the upright position, a correcting layer has to be added or subtracted for each inclination, in order to obtain this end. By employing the planimeter the necessary thickness of this layer can be most readily ascertained. Where a planimeter is not available the actual floating line may be obtained, after the model has been made, by cutting off layers, allowance having been made for this purpose. The same number of sections as before are then cut out to each of the inclined corrected water-lines, the paper model prepared and the centre of buoyancy obtained as already described. Through this new centre of buoyancy a line is drawn perpendicular to the inclined water line, and the distance between this line and the centre of gravity of the ship, already obtained, is the righting arm. If this process is repeated for each angle of inclination, it is thus seen a complete curve of stability may be approximately obtained. [Illustration: FIG. 16. MODEL IN UPRIGHT POSITION ] [Illustration: FIG. 17. MODEL IN INCLINED POSITION] A further method of arriving at results by experiment, involving principles not unlike those of the “paper section” method just described, has recently come under the author’s notice, and through the courtesy of its inventor—Mr John H. Heck, of Lloyd’s surveying staff at Newcastle—the following general description of the apparatus and fundamental principles is made public for the first time:— By means of a “stability balance,” roughly illustrated by Figs 16 and 17, in conjunction with either an outside or inside model of the vessel, the moments of stability can be practically determined. In practice, an inside model has been found the most convenient to employ. This consists of a number of rectangular pieces of yellow pine of any uniform thickness, out of which a portion has been cut, respectively to the form of the vessel at equidistant intervals of say 15 feet. These pieces, together with two end pieces, are kept together by four or six bolts, thus forming a contracted model, the inside of which is of a similar form to that of the vessel. If this model is filled with water to a height corresponding to any draught, it will represent a volume of water having the same form, and proportional to the displacement of the vessel at that draught.