1826.] English Books of Naval Architecture. 411 



just impost on their commodities, the merchants have sent to 

 sea ships of the very worst description. In the late inquiry on 

 this subject, several good approximate rules were given, of 

 which Dr. Young's was the best : his mode, however, did not 

 include the weight of the ship, and might soon be evaded when 

 burden was the consideration. Whether the duties are levied on 

 the articles, according to their bulk or to their weight, correct 

 calculations should be made of the spaces they occupy, or the 

 depths to which they cause the ship to sink, from an attested and 

 tried delineation of the vessel. 



The third article of the work before us is occupied in the con- 

 sideration of the centre of gravity of the ship. It is by no means 

 copious, including all extant that is valuable ; nor is there any 

 thing new in it. Dr. Inman's translation, with the exception 

 before-mentioned, has much more valuable matter on the subject 

 than it contains. 



The only methods worthy of consideration for determining the 

 point, are those I inserted in the Annals of Philosophy for Novem- 

 ber last, viz. that of considering the ship as composed of a 

 system of bodies, and finding the common centre of gravity by 

 the usual problem, and the mode of finding it by an experiment 

 on the ship. The latter mode of finding it has generally been 

 attributed to Chapman ; whereas Don Juan published it in 177 1,* 

 in the Spanish language, and it was translated into the French 

 in 1783, which is four years before it was inserted in the Swedish 

 Academy of Sciences. The proposition may be seen in Don 

 Juan's work, as translated by Leveque, p. 104, vol.ii. Although 

 recommended in 1793 in this country, it has not been undertaken 

 for any ship. In vol. i. art. 900 — 6, of Don Juan, there are 

 valuable problems apphcable to the same purpose. The new 

 solution 1 gave of the problem coincides in the result with Don 

 Juan's, and therefore it is fair to conclude that it is correct. 



In the second new mode of finding the centre of gravity of the 

 ship by experiment, as inserted with that just mentioned in the 

 Annals of November last, I perceive I have committed an over- 

 sight by taking the inclination to the horizon in one problem, 

 while 1 had used that from the upright in the former, which is 

 its complement. This rectification applied will make the dis- 

 tance of the centre of gravity of the ship from that of the 



,. , , , , Pa cosin. A — A A 



displacement equal to z^——. -r-. — . 



^ '■ r cosin. A — V sin. A 



There is another mode of finding the centre of gravity of the 

 ship by inclination, which I have not seen noticed by any author. 

 The following is a brief sketch of it. Let the ship be heeled 

 to the same angle by two separate horizontal forces, applied 

 at different heights in the plane of the masts. Then it 

 is evident that their moments of inclining power must be equal, 



• Tliisis pointed out by Mr. Read, in No. II, of a periodical work, entitled, Essay* 

 and Gleanuigs on JXaval Arcluttcturc ; puUbhcil liy bhcr\voyd and Cu. 



