ON PADDLE WHEELS. 161 



whether at light or load draught, in smooth water or high sea, he found the action of her 

 wheels to be uniform, causing but very little, if any tremulous motion in the vessel, or jerk to 

 the engines. As regards their durability, he considers that a vessel, if stationed abroad, taking 

 with her a small proportion of " spare spindles," as now fitted, with a spare set of " steel 

 collars " for the spindles, and " bushes " for the stems, she would be fully equal to continue 

 her service for any period (with the mechanical powers they might possess in the engine 

 department) that her engines might enable her to do. He states that owing to the twisting of 

 the spring beams, the crank head in the wheel lowered considerably, and altered the angles of 

 the floats ; but that was of course not to be attributed to any want of solidity in the wheels 

 themselves, nor did it do them any injury. There was no twist owing to the break in the 

 shaft, as has been supposed to be the case, on account of the inner frame only being immedi- 

 ately driven by the engine, for the paint was not disturbed in the joints where the spindles are 

 united to the frames, which must otherwise have been the case. In conclusion, Captain 

 Austin expresses his opinion that if the part of the vessel alluded to (the spring beams) were 

 properly secured, Morgan's wheels would be, as sea propellers, most valuable and perfect. 



4. Cave's Paddle Wheel. 



Plate LXXXI. Fig. 1., is an elevation of the first wheel made by M. Cave on his improved 

 construction : it is reduced from a drawing on a larger scale, which that gentleman had the 

 kindness to send from Paris, with a note stating it to be the drawing of the wheels fitted by 

 him in the year 1827, to the iron steam boat ' La Seine.' P, P, P, &c. is thepolyyon; r, r, &c. 

 the arms ; C the shaft in the centre of the boss ; A, A, &c. are the floats ; D, D, &c. the 

 stems ; h, h, &c. the guide rods ; B the excentric axis fixed to the side of the vessel, of which 

 the centre is at E, and which is sufficiently large to allow the shaft C to pass through it ; F 

 the revolving collar, turning on the excentric B ; and g the driving rod, fixed to the revolving 

 collar, and passing between two friction rollers k, k, attached to the polygon ; L L is the water 

 line. Now, since the point of contact between the roller and the driving rod must move 

 nearly in the circumference of the dotted circle, which is sometimes nearer and sometimes 

 farther from the excentric centre E, there results a difference in the velocity with which the 

 revolving collar is driven round : in the wheel represented in the figure the maximum velocity 

 is nearly double the minimum. This causes the great variations in the position of the different 

 floats and their guide rods, shown by the dotted lines in the figure : the floats are numbered 

 on the outer ring of the revolving collar, close to the pins by which their respective guide rods 

 are jointed to it; the numbers on the excentric axis show the positions which the cor- 

 responding pins take, and those at the extremities of the lower floats, the positions of the 

 respective floats when their spindles arrive at the same positions. These variations must 

 cause a great irregularity in the action of the floats, and it is evident that only one or two can 

 take approximately the required positions during their motion through the water. Fig. 2. 

 represents a wheel on Morgan's construction of the same dimensions as the former, in which 

 it was attempted to show, as in the other, the various positions of the different floats, but it 

 was found to be impracticable, the only variation sensible on this scale being that of the guide 

 rod Number 4, of which the positions are shown by dotted lines passing through the three 

 lower guide rods; the variations of the float were, however, imperceptible. The only 



