Royal InHitution of Great Britain, 427 



He prefaced his First Lecture (delivered on the 2d of May,) by 

 adverting to the commercial and other advantages which this coun- 

 try has derived from ships ; and in order that the terms which 

 he used might not be misunderstood by liis hearers, he gave^ 

 a succinct account of the leading principles of the science of theif 

 construction. 



To find the displacement of a ship is of the highest importance i 

 hence mathematical and mechanical means have been devised to 

 arrive at the fact, all of which have given way to a method intro- 

 duced by Chapman, a Swede, which is derived from the parabolic 

 curve, to which the lines of ships* bodies approximate. 



Stability is that property in a floating body which it exerts to 

 retain or regain an upright position when under the influence 

 of any force which tends to incline it. The comparative sta- 

 bility of ships may be judged by the distance of their centre of 

 gravity from a point called the metacentre ; — this was a disco- 

 very of Bouguer. Chapman has also given an easy but eleganl 

 method of finding this point, by a formula derived from the para- 

 bolic curve. 



The little which is correctly known of the resistance of fluids 

 was adverted to, and a remark made, that an important fact haiS 

 resulted from these inquiries ; that, ceeteris paribus^ the resistance 

 which floating bodies meet with in passing through a fluid, is as 

 the respective areas of their broadest section, and that the resist- 

 ances increase as the squares of the velocity. 



The relative proportions of masts and yards to the stability of 

 ships, and to the resistance to be overcome, next came under con* 

 sideration ; and, as the stability of ships increases with regard to 

 their breadth in a geometrical ratio, while, with respect to length, 

 it increases only arithmetically, so the length of the masts are 

 governed by the breadth of the ship, and the spread of yards by 

 their length. The general position of masts in ships of war was stated 

 to be, for the foremast ^ of the length of the ship from the stern^ 

 the mainmast ^, and the mizenmast ^ ; the length to be taken at 

 their line of flotation. 



The best proportion of length to breadth of three-masted ships 

 is 3.75 to 4 times their breadth; for length in brigs, 3.27 times 

 their breadth for length ; and cutters only 3 times as long as they 

 are broad. 



The foundation of the naval power of England was laid by 

 Alfred, who, to prevent invasion, designed himself a. fleet of galleys 

 which w^re, in jsize, and in every other respect, superior to those 



