On Skip-building. 169 



of their conimon centre of gravity from the load water line. Thus de- 

 noting the number of guns by A, he finds 



that the number of the crew may be represented by 3.763 A 4> 

 tlie weight of the crew by - - 10. 16 A -f, 



and their mechanical effect by - - 15 A |-. 



In like manner he represents by the formula 18^ A f, the provisions for 

 k months, and water for half the time. The displacement he likewise 

 connects with the weight of the guns, and ascends from thence to the stabi- 

 lity, — to the areas of the load water section, and of the main section of the 

 vessel, — to the position of the centre of gravity of the vessel, and even to 

 the movement of the sails ; — thus connecting every element of the ship 

 with the primitive element assumed. 



There are some, we can readily imagine, who will deny the possibility of 

 tracing all the elements of a ship to a primitive element, and to such we 

 would recommend the strong and forcible observations of the author of 

 the article on this most important point, and also the diligent study of 

 Chapman's Tables. We readily grant that the coefficients and exponents 

 by which the Swedish engineer has endeavoured to connect together the 

 elements of his inquiry, may in some, or even in many cases, be erroneous. 

 They may have been deduced from observations on too limited a scale to 

 permit us to draw in every case those general conclusions which are so de- 

 sirable ; but we quite agree with the author of the article, that a digest of 

 the properties of some of the best ships of the British Navy, conducted ac- 

 cording to Chapman's principles, would be productive of most important 

 results. In no subject, says oiir author, is there greater room for the ap- 

 plication of the most rigid principles of the inductive logic. Millions of 

 ships have been constructed, but only here and there a successful example 

 has been offered for our contemplation, as if to mock the implicit obedience 

 we pay in the practice of naval architecture, to uncertain and ill-defined 

 rules. 



One of the most important and valuable portions of this paper is that 

 devoted to the arching of ships. In every point of view in which the ge- 

 neral problem of arching can be contemplated, it will be found to involve 

 considerations of the highest importance to naval architecture. Owing its 

 origin to those peculiarities of form which the complicated conditions of 

 stowage, stability, velocity, and general sailing qualities render necessary ; 

 it has been a great object with the naval engineer to preserve to the float- 

 ing vessel unimpaired those essential properties of form which he en- 

 deavoured to impart to her in the process of building. Constructed as ships 

 are of timber of the most varied dimensions and forms, — disposed in di- 

 rections of so many different kinds, and subjected to strains so changeable 

 in direction and quantity, it may be fairly said, that, next to the original 

 determination of the best form, the skill and intelligence of the ship-builder 

 may be measured by the degree in which the tendency to arching may be 

 diminished. 



To discover the law, observes the writer of the paper, which influences 

 a ship, whether laden or unladen, when floating quiescently in water, we 

 may suppose the vessel to be divided into vertical sections of an indefinite- 



