110 ON THE STEAM BOATS OF 



velocity of the piston increased in like degree. We have already stated that the steam is 

 cut off, and thus caused to act expansively : the advantage thus obtained is analogous to that 

 derived from the same method in the pumping engines of Cornwall. 



As an accessory, and one of no little importance, we may mention the form of paddle wheel 

 originally introduced by the younger Stevens, but now universally adopted. The form of 

 this may be readily understood, by supposing a common paddle wheel to be cut into three 

 parts, by planes perpendicular to its axis ; that one of these being supposed to remain at rest, 

 the second is moved through one-third, and the third part through two-thirds of the space 

 intervening between two contiguous paddles. 



It seems to be conclusively shown by the researches of Barlow, that the modifications 

 of paddle which have been tried in Great Britain, are, upon the whole, inferior to the common 

 paddle wheel. The triple wheel of Stevens does away the principal objection which can be 

 opposed to the latter, namely, the long interval between the successive strokes of the wheel 

 against the water, and their violence. 



In vessels of small dimensions the same principle is applied, but the wheel is only double, 

 instead of being triple. 



The velocity of the pistons of engines used for manufacturing purposes is about 200 feet 

 per second. In the ' North America' this velocity was carried up to 384 feet, and the rate is 

 now exceeded in many of the newer vessels. Thus, in the steam frigate ' Fulton,' the velocity 

 of the piston is 450 feet, and in the ' Cornelius Vanderbitt ' and ' Highlander,' as much as 

 600 feet per second. 



We have enlarged upon the performances of the ' North America,' not from their being 

 unsurpassed, but in consequence of their forming an era in the history of steam navigation. It 

 was easily seen that the important part of the resistance, and which in fact seemed to oppose 

 an absolute barrier to all velocities beyond a certain limit, arose from the wave raised in front 

 of a vessel in rapid motion. 



Don George Juan estimates, that this cause of resistance increases with the fourth power 

 of the velocity. It was attempted to lessen this part of the resistance, by altering the form of 

 prows. False prows were therefore adapted to the vessels in use ; and, as the cavity left 

 behind the sternpost causes a similar resistance, false sterns have also been applied. These 

 attempts have been eminently successful, and in some instances no visible wave appears on 

 the water, before the entrance of the extreme breadth of the vessel. This is remarkably the 

 case in some of the newer steam vessels, in which the form has been derived from that 

 obtained experimentally by the addition of false prows and sterns. The latest model of this 

 description is that adopted in the new steam frigate ' Fulton,' a draught of whose water lines 

 accompanies this paper. (PI. cxvi.) 



A section of a vessel (the ' North Carolina,' PI. cxvu.) of similar form, but of less draught 

 of water, is also appended ; with a view of a third intended for sea navigation. 



In the models of this new class of vessels, although built with keels, there is only a few 

 inches dead rise in the midship section, and the floor extends, horizontally, nearly the whole 

 length of the keel. This form will be better understood from the draught of the steam frigate 

 Fulton.' 



A long flat floor had been used before in the ' North America,' ' Dewitt Clinton,' and 

 several other vessels, but differed from that of the new models in being nearly rectangular, so that 



