SECT, x.] OF STEAM NAVIGATION. 297 



3778-9 Ibs. for the resisting force ; consequently the power is 10 x 3778*9 = 37789 

 Ibs. raised one foot per second ; and as 550 Ibs. raised one foot per second is a 



S77SQ 



horse's power, the resistance is equivalent to -ggg- = 68'7 horse power. 



As ten feet per second is six nautical miles per hour, or nearly seven common 

 miles, and the power required is as the cube of the velocity, it is easily ascertained. 1 



OF THE METHODS OF PROPELLING STEAM VESSELS. 



624. Much of the advantage of steam power depends on its being commo- 

 diously and effectively applied to propel vessels. A slight review of these methods 

 will therefore enable us to judge whether or not the most effective and commodious 

 have been resorted to. 



The first and most simple and ancient method of applying a power within a 

 vessel to move it, is by means of oars, and the mode of combining them appears to 

 have been carried to a considerable degree of perfection. Oars, however, are not 

 at all adapted to move a large vessel ; they occupy too much space, and would 

 require too complicated a system of machinery to move them. Second : next in 

 simplicity, and perhaps also next in time, is the method of putting a wheel like a 

 water wheel, with paddle boards on each side of the vessel. This mode is now 

 almost universally followed. Third : an ingenious combination of parts has been 

 proposed, to be constantly under water, and to fold up into a small space when 

 they are moved forward, and spread when striking backward. Fourth : inclined 

 planes placed behind the vessel, and moved with an alternating motion. Fifth : 

 Daniel Bernoulli's method, proposed in 1752, consisting of planes immersed in the 

 water, parallel to the sides of the vessel, which, turning in a collar, were to be moved 

 in a plane, perpendicular to the keel. Sixth : a screw, resembling the water screw, 

 working in a cylinder entirely immersed in the water. 2 Seventh : or two spirals 

 or screws to work in opposite directions without a cylinder. 3 And lastly : a pump 



1 Some recent valuable experiments by John Macneill, Esq., C. E., show that the preceding 

 investigations and formulae for the resistance of vessels, (which are far from being clear,) are not 

 to be depended upon as accurate. See Appendix. ED. 



2 It was proposed by Mr. Scott of Ormiston. Dr. Thomson's Annals of Philosophy, vol. xi. 

 p. 438. 



3 This method was partially tried by Mr. Whytock, (Brewster's Philosophical Journal, vol. ii. 

 p. 39.) and is alluded to by Col. Beaufoy, who states it to have been brought from China ; and he 

 attended to see an experiment on a considerable scale, made in Greenland Dock by Mr. Lyttleton. 

 This gentleman had fixed to the stern-post of a Virginia pilot boat, a frame containing a large 

 copper spiral, which, by a winch turned by two or more men, gave it a rotary motion : the effect 

 was much less than expected, for, notwithstanding the boat was completely empty and considerable 

 exertions used, the progressive velocity did not exceed the rate of two miles per hour. 



2 P 



