250 Mr. W. G. Adams on the Application of the 



and B H two parallel radii on opposite rims of one wheel, C E F D 

 the axis Of two screw surfaces CEKGandDFLH of opposite 

 kinds, the outer edges GK and HL being at the circumference 

 of the wheel, and the angles which they make with H G at G and 

 H being each half a right angle ; C E, E F, and F D are equal to 

 one another, so that between the floats a vacant space is left 

 equal in breadth to either of them. KL is a rod connecting the 

 free corners of the floats, and the planes K E M and L F N are per- 

 pendicular to the axis. These two floats take the place of one 

 of the ordinary flat floats ; and I propose to compare the pressure 

 on them, and the power necessary to sustain it for a given speed 

 of revolution with the pressure, and the corresponding power, in 

 the case of the ordinary paddle-wheel. Before entering into the 

 calculation, it will be well to notice some of the peculiar features 

 of this paddle-wheel, which will probably prove to be not among 

 the least of its advantages. If it is possible to judge from the 

 conduct of a small model, they certainly appear to be decided 

 advantages. 



1. The floats enter the water gradually, the points K and L 

 being first immersed, and the whole gradually following ; so that 

 there is no sudden jerking of the steamer when a float enters the 

 water, as in the case of the ordinary wheel, where the jerking is 

 so violent at starting as to cause vibrations up and down by the 

 bending of the ship from stem to stern. The absence of this 

 jerking and the quivering motion will be no slight comfort to 

 those on board. 



2. These floats do not carry all the water before them, or cause 

 a strong backward current and so diminish the pressure on the 

 succeeding floats as in the ordinary wheel, but, as there is a vacant 

 space between the floats equal in breadth to one-third of the 

 breadth of the wheel, the water in this space is only slightly dis- 

 turbed, and this disturbance is not sufficient to cause any very 

 great motion at the point where the next float enters the water ; 

 also since the water runs off the floats both outwards and inwards, 

 and not in the direction of motion, there will be no large waves 

 formed in the wake of the ship ; so that the power which is ex- 

 pended in the ordinary wheel in producing large waves is in this 

 case usefully expended in increasing the speed of the ship ; this 

 is fully borne out in the case of Dr. Croft's working models ; 

 also the water thrown under the ship on both sides will help to 

 buoy it up. 



In these points it would seem that Dr. Croft's wheel is likely 

 to be superior to the ordinary wheel, whether the floats of the 

 latter are feathering floats or not. 



3. In the new wheel, when the float is coming out of the water, 

 the water runs off sideways readily, and is not carried up with 



