ON CYCLOIDAL WHEELS. 53 



and surface of board, which is at a great sacrifice of speed when the vessel is in still water, 

 a condition to which the same vessel is of course liable ; and hence arises the disadvantages 

 and loss of power of the ordinary wheel for sea purposes. 



CYCLOIDAL WHEELS. 



The vertical wheel, although possessing in its action the advantages we have pointed out, is 

 however attended with several serious practical objections. To effect the vertical position of 

 the paddles, considerable complication is necessary in the construction, and a great number 

 of moving parts are required, which are not only attended in the commencement with a great 

 outlay, but require continual repairs, and are liable to derangement. 



These objections have led to attempts to improve the action of the common wheel by a 

 different arrangement of the paddle boards, which have been so far successful in the cycloidal 

 wheel, that its use is very likely to become general and supersede that of Morgan, from its 

 superior strength and simplicity, while it does away with most of the evils to which the com- 

 mon wheel is subject. A patent for a cycloidal wheel was first taken out by Mr. Galloway, 

 in August, 1835 ; but as it appears that a similar wheel was employed by Mr. Field, in a 

 vessel on the Thames, in the year 1833, and a model of a cycloidal wheel exhibited to the 

 Lords of the Admiralty in the same year, (see ' London Journal,' December, 1835,) we 

 conceive that the credit of the invention rests with the latter gentleman. 



The principle of this contrivance consists in dividing the paddle into a number of parts, 

 which are placed upon the wheel in the curve of a cycloid, so that they enter the water at the 

 same spot, and follow one another so rapidly as to cause little resistance to the engine on 

 entering the water ; and afterwards separate, so as to afford full scope for their action in passing 

 the centre, and in coming out allow the water to escape readily from them. A drawing of the 

 cycloidal wheel, fitted by Messrs. Maudslay and Field to the Great Western steam ship, is given 

 in Plate xxvi. Fig. 9. The dotted circle is that which I have termed in the preceding investi- 

 gation the rolling circle, the velocity of its circumference being equal to that of the vessel : the 

 action of the paddles will be truly represented by the motion of this circle on the horizontal 

 line. The paddles are placed in the direction of the curve A B, which is a portion of a simple 

 cycloid described by the point A in the circumference, or by a fixed point at B during the 

 rolling of the circle along the line, and must therefore enter the water at the same spot. 

 When immersed, they no longer follow a common direction of motion, but gradually separate, 

 so that in passing the vertical position they do not in any way interfere with each other's 

 action, and resembler so many small radiating paddles. After passing the centre, they still 

 continue to separate in their direction of motion, and consequently leave the water very freely, 

 and without the back water to which the common wheel is subject. To enable the reader 

 to understand the beautiful action of this wheel, we have drawn the positions of the paddles 

 in a vessel in motion, at equal intervals of time, (Fig. 10.) as has already been shown in the 

 common wheel, from which will be seen its great superiority both in entering and leaving the 

 water : it enables an engine in any weather to make a greater number of strokes, by throwing 

 more work on the bottom paddles ; and reduces considerably the shock on entering the water, 

 which is not only productive of a loss of power, but is very unpleasant to the passengers. 



