140 PLYMOUTH INSTITUTION. 



January 22nd. — Mr. Ciiatfi eld's third Lecture on 

 Naval Architecture. 



The lecturer observed that, on referring to his two former pa- 

 pers, he found that there was a great deal of matter yet untouched, 

 lie had explained the leading principles in the theory of naval 

 construction, and had described, in a summary way, the mechan- 

 ical mode of ship-building: he had also treated on the "moving 

 forces" employed to propel vessels, more particularly the action 

 of the wind vtpon a ship's sails — and had illustrated the principle 

 upon which ships, by a series of diagonal movements, work to 

 windward of the place of departure. 



The lecturer considered that from the period at wliich we find 

 a ship built upon the "stocks" until the lime of her being acted 

 upon by the moving forces employed to propel her, many operations 

 are performed in the department of naval architecture which might 

 witli propriety, occupy one of the evenings of the Institution. 

 He therefore proposed to speak, first, of the principle and mode 

 of launching ; and then, of the manner in which the stowage and 

 internal arrangements are planned and proceeded with. 



1. The lecturer described, by means of a very complete model, 

 the whole process of fitting a launch ; he actually launched the 

 model, and thus elucidated the operation of constructing a 

 " cradle,' capable of sustaining the entire weight of the ship 

 when all other support is removed, and which is so contrived as 

 to move with the vessel until she is safely in the water. The 

 system of launching was shewn to be exceedingly simple ; but 

 the details are too numerous to admit of repetition in the short 

 outline which we are enabled to give of the lectures of the Insti- 

 tution. 



2. The lecturer proceeded to treat on stoivage, which signifies 

 the method of arranging the posit ioiiSj and subsequently disposing 

 of all great weights — viz., the ujumunltion, provisions, diud stores ; 

 with a view to promote tliose good qualities which, when com- 

 bined, constitute excellence in naval construction. A vessel's 

 stability under canvass, the easiness of her evolutions, and her 

 durability, are all affected in an important degree by the system 

 of stowage. Here the lecturer described the mode of determining 

 the trim of a vessel, or her " seat" in the water; which depends 

 on the relative positions of the weights before and abaft the 

 centre of gravity of the volume of water which the naval architect 

 designs his ship to displace, when equipped for sea. But the 

 predicted " line of floatation" may be adjusted under a variety 



