356 Analysis of Scientific Books and Memmrs. 



has had high and transcendental curves applied to its diflferent parts, may 

 have had all its properties altered the moment the vessel was launched. 

 The beams imperfectly attached by their ends to the sides of the ship 

 would occasion transverse alterations of form ; and the unequal action of 

 the pressure and the weight producing, by tagging or hogging, those great 

 alterations of form longitudinally, which in many instances have obtained 

 for our men-of-war the epithet of broken-backed. Most of our readers are 

 aware, that, in the ordinary constructions of carpentry, the figure at first 

 devised by the workmen is not often ultimately attained. In the com- 

 monest roof, what diflSculties seem to be in the way to meet the action of 

 gravitation on the timbers, and the diversified strains produced by its 

 power ! It is one thing to join together a system of timbers, and another 

 to estimate the best form of their combination. It is not always the quau' 

 tity of material that may be employed in a mechanical construction which 

 imparts to it strength, but the disposition of its component parts. Ten 

 load of timber in the hands of Seppings would produce a resultant having 

 greater mechanical advantages, than twenty employed by some of his pre- 

 decessors. Some men imagine that strength is only to be gained by the 

 employment of heavy masses, not considering that the nature and quantity 

 of the strains acting on them may entirely disturb their arrangement. We 

 remember an English squire once endeavouring to persuade us that the 

 gates of A z* county were the best, because they were rectangular filled with 

 vertical bars, and incapable of being resolved into any form but that men- 

 tioned. The notion of a triangular combination of timbers, and of the 

 invariable form which such a combination preserves, was unknown to him. 

 The strength was obtained, so said this rich agriculturist, by the parallel 

 bars, and the efficacy of one in a diagonal direction was gravely doubted. 

 At that time, however, neither the Royal Institution, Mechanics Insti- 

 tutes, or^the Society for the Encouragement of the Useful Arts, existed. 

 Men combined together timbers, but without inquiring after the legitimate 

 laws on which all such combinations should be founded. Sir Robert Sep- 

 pings found our dock- yards much in the same way. One generation of ship- 

 wrights had succeeded to another, and each was content with the labours of 

 its predecessor. Timber in abundance was supplied by the liberal grants 

 of Parliament, but science had little to do with its consumption. Forests 

 were levelled to satisfy the demands of a vigorous and long and protract- 

 ed war ; and the lofty bends of timber which constituted the frames of the 

 ships which conquered Copenhagen and the Nile, were, like the country 

 squire's gate, disposed in enormous parallel arrangements bearing imper- 

 fectly on each other, and deriving a large proportion of their support from 

 the planking alone. Here then was a field open for the ardent enterprize 

 of some one capable of surveying the mighty fabric of a ship in all its com- 

 phcated relations ; — some one whose mind was freed from the uncertain 

 rules that guided his forefathers, who could contemplate the whole with 

 the eye of a mechanical philosopher, apply to it all the beautiful relations 

 of strain, pressure, and force, and courage, to withstand all the opposition 

 which such a great innovation must necessarily raise. The rectangular 

 disposition of the timbers hence gave way to oblique braces and riders 



