In the last column of this table is the breadths of the different ships in proportion to their lengths. In the ships of three decks, the relative breadths of the ships of the different nations is in the following proportion and order: of the Spanish ship 122• of the Swedish 71, of the French A-g, and of the English where the relative breadth of the Spanish ship is seen to be the greatest, and of the English ship the least. In the large class of ships of two decks, of SO guns and upwards, the relative breadth is in the following proportion and order: of the Spanish ship the Danish IN, of the Swe dish Vg, of the French ;..”. and of the English where the relative breadth of the Spanish ship is seen to be the greatest, and of the English ship the least. The difference, however, in the relative breadth of the last two, the French and English ships, is very little, and if some other French eighty-fours had been taken instead of the Tonnant, the relative breadth of the French and English ships of this class would have been the same, the Ganges having been built alter a French ship. the Canopus. In the smaller ships of two decks, the relative breadth is in the following proportion and order: of the English 1V1, of the Span ish, Swedish and French and of the Danish ;41; where the relative breadth of the English ships is the greatest, and of the Danish the least. In the frigates, the relative breadth is in the following proportion and order: of the Spanish ship pa, of the French Unite (while in the French service, the Impericuse) of the English Latona (one of a numerous class in our service, built after the old LedaM-2, of the Danish A37, of the Swedish pg, of the French Niobe and of the English Portland where the relative breadth of the Spanish frigate, is seen to be the great est, and of the English 60 gun frigates the least. The relative breadth of the French frigates taken during the last war, is generally nearer that of the than of the Unite.
From this comparison, continues Mr. Morgan, it appears that the relative breadth of nur 120•gun ships is less than that of the three-decked ships of the other nations; that the relative breadth of our large class of two-decked ships agrees nearly with that of the French, and is less than that of the ships of the other nations; and that the relative breadth of the 60-gun frigates is considerably less than that of the frigates of other nations, and of most of our own frigates. The relative breadth of the Latona stands high in the order of the ships of their respective classes.
It does not appear, from this table, that any regu larity exists in the proportion between the length and breadth of ships according to their magnitude. Whether ships, as they increase in magnitude, should have greater or less relative breadth in proportion to their length, does not appear to have been attended to as a general principle in the designs of the ships of different nations. In the Spanish ships, the relative breadth of those of,three decks is greater than that of the ships of two decks, and the relative breadth of the larger Spanish and Danish ships of two decks is great:.
er than that of the smaller ships of two decks, and the relative breadth of the two-deckers is greater than that of the frigates. In the ships of the other na the contrary is more frequently adopted, al though very irregularly.
The first consideration respecting the relation be tween the length and breadth of ships of different magnitude, is, whether large or small ships require the greater relative stability. Now suppose a larger and smaller ship to have their moments of sails in proportion to their stability, and the height of their lower tier of guns to be the same from the water's surface, when they are upright; while these two ships would then be inclined, by the force of the wind on the sails, to the same angle, this inclination might he dangerous to the larger ship, but quite safe to the smaller ship. the sides of the two ships above the wa ter being immersed nearly in proportion to their breadth. Supposing the breadth of the larger ship to he 50 feet, and of the smaller 40 feet, and the height of the lower ports in both ships to be six feet from the water's surface, when the lower ports of the small er ship are, in consequence of the inclination, two feet from the water, the lower ports of the tarter ship arc only one foot from the water.
Supposing that the moment of sails is given in a proper proportion in the smaller ship, a smaller mo ment of sails in proportion to their relative stability must either be given to the larger ship, or a greater moment of stability, retaining the same moment of sails. For the sake of velocity, it is desirable that the stability of the larger ship should be increased.
Suppose the two ships to be similar, the one carry Mg two tiers of guns, the other three. The stability being in the proportion of the fourth power of the simple dirnetisions, if' the centres of gravity of the two ahips were raised above the centres of gravity of the displacements only in proportion to the dimensions o1' the ships, the stability of the larger ship would be increased in a much greater proportion than in the smaller ship; bat as the (emir( of gravity in the large ship is raised by the additional deck and tier' of guns higher' than in the proportion of the dimensions, tire stability is increased in one way and diminished iu another. The effect of these clenu'nts of the stability on the value of its moment should he correctly ascer tained. irobably, ou the whole, the stability of the larger ship may generally be rather increased than diminished by the alterations, but not sufficiently without a little increase of relative breadth. This, however, could he obtained by calculation and expe riments on other different classes of ships, and would be ti•aluable information Ion- the (leterrnination of the i•e •ative dimensions of shipa of different sizes.