146 APPENDIX. 



a groove or other guide fixed to the side of the vessel (as in Symington's wheel), or in the 

 interior of the wheel itself (as in Steed's, &c.). Time will not permit us to give a full 

 description of any of these wheels, nor to enter into any calculation of their effect, which 

 must, however, be quite unnecessary ; for a machine tried under such favourable circumstances 

 as Symington's wheel must certainly have been adopted, if it had any claim to preference. 

 A wheel, on a similar principle, with the paddle cranks guided by cams in the interior of the 

 wheel, was tried some years ago in a small boat on the Thames ; but the friction was so great, 

 that three or four men could scarcely prevent the boat from being carried down by the tide, 

 although they could easily have rowed her at a moderate speed. The friction of the feathering 

 machinery must in all cases be very considerable ; so that, however beautifully it may work at 

 the beginning, there is no doubt that its action would soon be impaired by wear, and it would, 

 perhaps, not require a long time to be entirely destroyed. 



B. Paddle Wheels with floats turning on horizontal axes or spindles. 

 1. Buchanan's Wheel. 



The principle of this wheel is described by the patentee in his specification in the following 

 manner : 



" In the first place, my said invention is established upon a mathematical theorem, which 

 " may be enumerated in the words here underlined, namely : If two equal rings or circular 

 " lines be conceived to revolve, each upon its respective centre in its own. plane, with one and the 

 " same uniform velocity, and in the same direction with regard to parts of the lines or rings alike 

 " situated, and any point be taken in one of the rings or lines, and a right line be drawn from 

 " that point parallel to a line supposed to join the centres, until it meets the other line or circle, 

 " then I say the right line so drawn will be equal to the line of distance between the centres, and 

 " will continue equal and parallel to that line of distance during the whole of every revolution 

 " so made." 



Fig. 1. PI. LXXVI. is a diagram of Buchanan's wheel, which has been drawn of the same 

 dimensions, and with the same number of floats as those of the ' Phoenix' and ' Salamander.' 

 From the centre of a framing similar to that of the common wheel, and called by the patentee 

 the Pitch wheel, r, r, r, are the radii or arms ; S, S, S, spindles, working in bearings in the cir- 

 cumference of the Pitch wheel ; each spindle is attached to a float, represented in the diagram 

 by the straight line A B, which is divided into two equal parts by the spindle, one end of 

 which passes through the Pitch wheel, and is furnished with a lever or crank S G. The ex- 

 tremity G of this lever is bent at right angles to S G, and works in a bearing on the circum- 

 ference of a flat wheel or frame G G G, called by the patentee the Connexion wheel, which 

 turns on an axle fixed to the ship's side, excentrically with respect to the Pitch wheel, its 

 centre being situated at a different point. This axle is made sufficiently large to admit of the 

 shaft passing through it. The crank S G is equal in length, and constantly parallel to the 

 line that joins the two centres. 



The float, being fixed to the crank, must evidently remain constantly parallel to a fixed 

 straight line during the whole of each revolution of the wheel, nor can any alteration in the 



