MR. J. C. DYER ON STEAM NAVIGATION. 289 



Dr. Franklin, in 1785, writes to Monsieur Alphonse 

 Leroy thus : — '^ Several projectors have at different times 

 proposed to give motion to boats, and even to ships, by- 

 paddles placed on the circumference of wheels on each 

 side of the vessel ; but this method has been found so in- 

 effectual, as to discourage a continuance of the practice'^"^. 



The plan proposed by Daniel Bernoulli, in 1783, was 

 by driving a column of water out at the stern of the vessel ; 

 which plan has been many times suggested, and several 

 times tried by other ingenious men, but without success. 

 It seems strange that, to so eminent a mathematician as 

 Bernoulli, the radical defects of this plan should not have 

 occurred. As the water issues from the mouth of the 

 tube, it escapes in the radial lines of a semisphere. The 

 resisting forces will be directly as the distance of each of 

 the radii from the surface, and their propelling power will 

 be equal to the force with which the water is driven from 

 the orifice, only in the direct line of the tubers centre, and 

 it will diminish with the angular deviation of the radii from 

 that line, until it becomes nil at right angles; wherefore 

 this mode of pressing water against water (though simple 

 and plausible at first sight) is the most wasteful expen- 

 diture of propelling force of any that has been proposed. 



It appears that " endless- chain floats " have been many 

 times proposed and patented ; but this plan, too, is de- 

 fective in principle, and has always failed in practice. 

 The chain-floats are driven horizontally, and successively 

 acting upon the same column of water, generate a current 

 in the direction of their motion, and much of the pro- 

 pelling power is lost by moving and agitating the water. 

 In an experiment I witnessed in 18 13 (in a boat on the 

 Bridgewater Canal) , the floats were placed about four feet 

 apart, and when first started, the boat moved with con- 

 siderable speed ; but as the speed of the floats increased, 

 * Life of Dr. Franklin, vol. iii. p. 528. London, 1818. 



SER. III. VOL. II. U 



