ON PADDLE WHEELS. 143 



more work was done at much less expense with Morgan's wheels than with the new ones. 

 The dip of the floats in the former case was 5 ft. 8| in., and the height of the axis above the 

 water only 3 ft. 1 in.; in the latter case the dip was 3 ft. and the height of the axis above 

 the water 5 ft. 5 in. 



The new steam frigate ' Gorgon,' of 1100 tons, has lately been fitted with a pair of Field's 

 wheels, and was tried a short time ago without her masts, drawing 13ft. 6 in. mean. The 

 wheels made 20J revolutions per minute, and a mean speed of nearly lOf miles was obtained, 

 which gives about 7 ft. 4 in. for the radius of the rolling circle, the extreme radius of the wheel 

 being 13 ft. 3 in. The paddle boxes here were also made for Morgan's wheels, so that 

 sufficient width could not be given to those afterwards made for the vessel. This disadvantage 

 must, of course, be taken into account in estimating the value of a wheel. This wheel being 

 now very extensively employed, experience will soon show whether there is any advantage 

 in it or not. Among the principal vessels fitted with these wheels, besides those already 

 named, are the 'Great Western' and the 'British Queen' American packets, and the 'Hermes,' 

 a government steamer of 730 tons. 



3. Paddle Wheels with oblique floats. 



Such wheels have been tried at various times and under various forms, some of which have 

 been patented. Among these may be named, as the most simple, that for which Mr. Samuel 

 Hall obtained a patent in June, 1836. In this wheel the paddle boards, instead of standing 

 at right angles to the rims and parallel to the axis of the wheel, as in wheels of the ordinary 

 construction, are placed obliquely to the rims and to the axis of the wheel. The subject of 

 the patent is not, however, the use of oblique floats, but the making of one-half of them to 

 enter the water in one diagonal direction, and the other half to enter it in the reverse diagonal 

 direction, or in large paddle wheels, making the boards change their direction of entering the 

 water four times instead of twice. We do not think that any effect can be produced by 

 giving the floats different positions, but that the action would be about the same as that of 

 the ordinary paddle wheel with oblique floats, in which they all incline the same way ; and it 

 has been found by experience that this requires a greater surface of paddle board than the 

 common wheel to produce the same effect, which can also be demonstrated theoretically in 

 the following manner : 



The circumferential velocity of any given point of a float of the common wheel being V, 

 and the velocity of the vessel v, we have already seen that its effective velocity is V v cos. $, 

 and that the pressure upon it is proportional to [V v cos. ] 2 ; but, with the same given 

 velocities, the effective velocity of a point of an oblique float, situated on the radius which 

 passes through the middle of the float, and at the same distance from the axis as the given 

 point in the common wheel, is only [V v cos. </>] cos. , if a is the angle which the surface 

 of the float makes with the axis of the wheel. The corresponding pressure is therefore 

 proportional to [V v cos. </>] 2 cos. a 2 ; and, the width of the wheels being the same in both 

 cases, the ratio of the tangential pressure on the oblique float to that on the common float is 



POS Q? 



- , supposing the whole of the former to radiate from the axis, which is only true for 

 the middle part ; but that will not affect the reasoning, as it might easily be shown that there 



