BRITAIN.
To Mr. Fulton, however, belongs the great honour of having been the first w ho endeavoured to investi gate on principle, the difficulties of the subject; and it is remarkable, that he derived his data from the expe riments of the society for the improvement of naval architecture, a brief' allusion to whose most useful la bours has been already made at the end of the part devoted to resistance. M. Marestier, in an able re port on the steam navigation of America, drawn up by command of the French minister of marine, and published at Paris, in 1824. has described at some length his method of proceeding.. It is in principle this: having determined the resistance of the vessel, he inferred that the paddles must experience the same resistance, and that the engine must exert a force at the centre of effort of the paddles, equal to the resistance of the paddles. Assuming then the velo cities of the piston and paddles as known, and equiv alent to V and r, and the forces on the same as equiv alent to F and j, he formed the proportion V: v: :f: F; and by dividing the whole force on the piston, by th,t force exerted by the steam on any given portion of its surface, he obtained the surface of the piston itself, and thence its diameter.
Knowing then the whole resistance on the paddles, and supposing only one paddle on each side to act at the same instant, the area corresponding to that re sistance becomes known, the half of which determines the surface of one paddle. Knowing also from the number of strokes made by the piston, the number of revolutions made by the paddle wheels, the diameter of the wheel may be determined so as to ensure to the paddle the velocity originally assumed. Fulton hav ing in this manner determined the force necessary to propel his boat, and accurately considered the mode by which it might be most successfully applied, avoid ed the great error of his predecessors, viz. attempt ing too much with an inadequate power, and gave to steam navigation that splendid and triumphant char acter which it now possesses; so that within little more than the half of a century after so transcendent a philosopher as Bernouilli had declared the utter im probability of its success, and within less than twenty years after its first successful attempt, has steam nav igation arrived at such a perfection, that even a voy age to India has been accomplished, and a passage across the Atlantic, by no means regarded as an un common thing. What other achievements it is
destined to perform, time must develop.
The form of a steam boat must in some degree assi milate to that of a sailing vessel, but there are many peculiar circumstances to be taken into account in considering of their construction; such as the partic ular kind of navigation for which they are destined— whether for the open sea, or for the shallower waters of rivers and lakes. If for the former an increased draught of water becomes necessary; but for the latter this element must be less considerable.* These considerations are to be inferred from the experiments on the resistance of fluids, in which it has been prov ed, that the quantity of water beneath the body in mo tion, has a very important influence on the resistance it experiences; and also, that if the water be at all con fined the resistance is very considerably increased. This circumstance indeed is one of common observa tion among watermen; and it has been moreover ob served in steam boats of different sizes on the same river, that as long as the water continued shallow, the smaller boat has had the advantage; but as the water has gradually deepened, the velocity of the larger boat has increased. A similar observation applies to the area of the midship section, which it is necessary to have as small as possible in boats destined for canals or narrow rivers, since the resistance depends on the relation of the area of the section of the boat, to the area of the section of the fluid.