PLYMOUTH INSTITUTION. 141 



of modifications, because the mere libration of weights which 

 keep each other in equilibrio depends on their relative (not their 

 actual) situations, in reference to the axis of rotation : conse- 

 quently, the "trim" of a ship alone, is not the only principle 

 which a naval constructor has to consider. 



A ship floating in a quiescent, stkte will be liable to strain, 

 unless the distribution of the weights on board be regulated by 

 the vertical pressure of the water under the vessel's bottom 

 which varies according to the form of the submerged part of the 

 body, from one extremity to the other. An example was quoted 

 by the lecturer, of the effect of this principle in actual practice, 

 (on a 74 gun ship) as given by Dr. Young, in a paper published 

 in the Philosophical Transactions, 1814. The argument was then 

 applied to a ship in motion, the lecturer demonstrating that the 

 weights at the extremities of a ship cause her to plmige into the 

 sea with a force proportional to the squares of the distances of the 

 weights from the centre of rotation : hence it follows that ships 

 become strained by loading them with heavy weights towards 

 the extremities, by which they are not only torn to pieces, but 

 their progress through the water is materially impeded. 



The lecturer invited the attention of the society to some 

 general rules by which the required cavity of a ship's hold may 

 be correctly estimated, and subdivided. He read, from official 

 reports on ships' qualities their various characters as regards their 

 capabilities for s^owd/^*-^ ; and thus proved that even in vessels 

 of the same '^ class," their characters are widely different. Some 

 vessels bear the character of stowing an unusual quantity of 

 w^ater: others will stow a particularly large proportion of bread : 

 others have a very capacious after hold, spirit room, magazine, 

 and so forth : at the same time many ships are respectively defec- 

 tive in one or other of these particulars. Facts of this kind re- 

 flect on the naval architectural department ; they certainly betray 

 a want of method: because, if a ship will stow water, or 

 bread, or any other species of provisions, for a given period ; it 

 should follow as a thing of course, that her capacity for stowage 

 be perfect in every other particular for the same length of time. 

 In the opinion of the lecturer, such would be the effect of a sys- 

 tem founded upon rules of proportion, which it would be his 

 endeavour to make clear. He took his position upon the " Re- 

 gulations of the service," by which he perceived that a very me- 

 thodical arrangement may be made for determining with precision 

 the relative magnitudes of all the compartments for stowage. 



