of Ships of the Line. 227 



we shall now proceed to inquire how far the displacement is 

 affected by the same datum. 



It is, or ought to be, an object of great solicitude, when the 

 design of a ship-of-war is formed, to make its whole force 

 available and effective, not merely in still water, but also when 

 the sea is much agitated, and the power of the wind on the 

 sails is such, as to produce a considerable inclination from the 

 upright. Under the latter circumstances, if the lower ports be 

 so depressed as to be below the waves, Vve lose the services of 

 the lower battery in action, or at least fight its guns with very 

 great inconvenience and liability to disaster. To prevent such 

 bad consequences, it is absolutely necessary, in the construc- 

 tion, to give to the ports a due elevation above the assumed 

 plane of floatation, and, with this plane as a base, to obtain 

 a displacement, whose buoyancy shall be equal to the weight 

 of the ship when ready for sea. If this precaution be not 

 attended to in the first instance, the constructor must inevitably 

 labour under all the anxieties attending a distracting uncer- 

 tainty and a fearful looking for of failure in a vast and expen- 

 sive structure. Every attempt at an after adjustment, in this 

 particular, will produce not only a deterioration of some other 

 important quality, but a general vitiation of the design ; and 

 nothing but a complete acquaintance with the rationale of his 

 art can enable him to proceed with confidence and precision. 

 It is true, that in the present state of science, the physico- 

 mathematical laws of naval construction cannot all be derived 

 a priori; but those which cannot, may be developed by the 

 analysis of ships. The inductive method must naturally be 

 disagreeable to those who are in the habit of mistaking self- 

 confidence and fancies for real knowledge and well-founded 

 deductions ; but it is the only one capable, from its accumu- 

 lation of data, of conducting us with certainty in the path 

 of improvement ; and, with the corps of naval engineers which 

 this country now possesses, it is to be very much regretted that 

 the energies of some of them are not, under proper authority , 

 directed to the permanent prosecution of an undertaking so 

 pregnant with advantage, as the analysis of the ships of the 

 British navy. We have seen quite enough of the blind efforts 

 of ignorant mystics and pretenders to be fully satisfied of the 

 impotency of quackery, and to lament, that our leading naval 



