HISTORY OF MARINE ARCHITECTURE.

39 *

contributive to the excellence of a ship. The forward situation of the extremebreadth in fig. is similar to its position in i>, but it resembles the form generallygiven to a ship’s bow, much closer than the preceding, the forebody, which is ofthe same length with the last, being formed by the segments of two circles. Theresult perfectly accords with reasonable expectation, the velocity is encreased to7.351, being 346 above, and its motive power diminished to 42.17, or 17.56,below the former ; a circumstance plainly demonstrating the necessity of a properswell being given to the bow or fore-body, provided other essential points are, atthe same time, attended to, and the required addition, or what is called by ship-builders fullness, is not carried to an improper and extravagant height. The truthof this becomes fully established, by the experiments made on fig. k; the forebodyof which answering the description just excepted against, being a semi-cylinder, itsvelocity consequently becomes diminished to 7*223, or .128 below i, while itsmotive weight is augmented 1048,26, or 6-.09. Fig. /, has the same fore-body;but its after-body * considerably lengthened, a measure which diminishes the rate

to

* “ The bodies used in the years 1796 and 1798, (says the report) were respectively immersed tothe depth of six feet under the surface of the water. In order, therefore, to make comparisonsbetween the same bodies, considering them as ships, it may be found necessary to deduct the friction,which takes place against the top surface of the said bodies, and the remainder will establishthe resistance sustained by the said bodies, considered as the immersed part of ships or navigablevessels.”

The bodies ABCDEFG, a b c, plate the first, were constructed for the purpose of ascertainingthe advantages and disadvantages arising from their differently formed stern ends. By inspecting,therefore, the resistance on the bodies A B, it will be found that the resistance of B is a little less thanthat of A, also that the resistance of k is a little less than that of l ■. a curious circumstance, whicharises from the stern ends of A and m, having a greater surface for friction than those of B and /.From thence it is evident that the encreased resistance arises from the friction against the stern ends ofH and m, being greater than that of the friction, and minus pressure together of the stern ends B and 1 .It must however not be forgotten to be observed, that the figure C, plate the first, consideted as a ship,has less Resistance in the descending velocities, from five nautical miles per hour, than B ; but in the supe-rior rates of six, seven, and eight miles per hour, B experiences the least resistancee. This apparentlyparadoxical variation, is occasioned by the stern resistance, in the instance of the after body of Cincreasing, in a greater ratio, than in the case of B, a circumstance which probably arises from the an-gular part of C, in the after body, or stern, being more obtuse than that of B. The cause is obvious.

In respect to the bodies DE, &c. to c, it appears they have all greater resistances than AB or C ,disadvantages which evidently arise out of the form given to their after-bodies respectively, from amongwhich that of G is the worst of all. The bodies B defghikm, were constructed for the purpose ofascertaining the comparative advantages and disadvantages arising from the different formation of the

3 H 2 fore-body ,