1825.] Plans of Ships in the British Navy. 325 



considerable progress in them, and exercised his knowledge with 

 great effect. He appears to have applied himself with much 

 energy to the study of the formation of ships by observing the 

 effects of their different forms and equipments, after a similar 

 plan to that laid down in this article, though not with such great 

 advantages as improved calculations since afford, nor on so 

 ample a field for observation as an analysis of the British navy. 

 Neither did Sweden in the time of Chapman produce a corps du 

 genie maratime of thirty students of naval architecture, of good 

 mathematical attainments, and who have been devoted to the 

 study of all the problems of the theory, as well as being ac- 

 quainted with the practice of ship-building. 



The plan is equally applicable to steam vessels. The French 

 have already done this, by sending a mathematician of the name 

 of Marastier over to America, in 1823, who has given the ana- 

 lyses of above 100 steam vessels, with a theory derivable from 

 •them. 



The knowledge of the place of the centre of gravity of the 

 ship and its contents, is of the greatest consequence. Most 

 mathematicians have agreed that it is the centre of rotation in a 

 ship. Without knowing it, the stabihty cannot be measured in 

 any case. It has not been found in this country on more than 

 two ships. By calculating the moments of the weights from a 

 horizontal plane, and dividing by the whole weight of the ship, 

 the point was ascertained on the Bulwark and on the Ajax, at 

 the School of Naval Architecture, under Dr. Inman, in 1817. 

 It was found to be at four feet five inches from the ports in each 

 case nearly, or at one foot seven inches above the channel ser- 

 vice water-line. In obtaining the point in this way, the objec- 

 tions are, the method is very long, and the specific gravity of 

 wood differing at sea, from absorption and exhalation, it is liable 

 to errors. The vertical moments are, however, highly useful for 

 more than one purpose. The time of its calculation for each 

 ship was two persons for a year each, besides the assistance of 

 labour in weighing many of the component articles, as stores, 

 blocks, &c. 



To find the point at any period of a ship's service without 

 regard to the specific circumstances of each component weight, 

 must evidently be a most important acquisition. This was first 

 proposed to be done by an experiment on the ship itself by 

 Chapman, the eminent Swedish naval architect, in 1793. It 

 has not been undertaken in this country for any ship. Chap- 

 man's mode of ascertaining the point has two objections belong- 

 ing to it. He uses the metacentre as a measure of stability at an 

 angle of 8° or 10°, which is decidedly erroneous. This is, how- 

 ever, easily corrected by substituting Atwood's equation of sta- 

 bility for it. The second objection is, that he has overlooked, 

 apparently, the change of place of the centre of gravity of the 



