THE MOTION OF STEAM VESSELS. 331 



wheel; for in consequence of the total resistance to all the paddles being so much 

 less than in the common wheel, much greater velocity is required to obtain the re- 

 quisite pressure, which is attended with the consumption of an additional quantity of 

 steam, and of course of a proportionate loss of power. 



This loss of power is most sensible when the wheel is slightly immersed, as may be 

 seen from the Table ; whereas the lost power from the oblique action of the common 

 wheel is then scarcely perceptible. When the vessel is more immersed, and the angle 

 of inclination at which the paddle enters is greater, the proportion of lost power in the 

 common wheel is much increased, while that of the vertical paddle remains nearly 

 constant, so that in cases of deep immersion the vertical paddle has considerably the 

 advantage. 



5th. That in any wheel the larger the paddles the less is the loss of power, because 

 the velocity of the wheel is not required to exceed that of the vessel in so high a de- 

 gree in order to acquire the resistance necessary to propel the vessel. 



6th. That with the same boat and the same wheel no advantage is gained by re- 

 ducing the paddle, so as to bring out, as it is called, the full power of the engine ; 

 the effect produced being simply that of increasing the speed of the wheel, and con- 

 suming steam to no purpose. 



7th. That with the same boat and the same wheel an increase of speed will be ob- 

 tained by reducing the diameter, or by reefing the paddles, at least within certain 

 limits, viz. as long as the floats remain immersed in the water, and the velocity of the 

 engine does not exceed that at which it can perform its work properly. The increase 

 of speed is in the ratio of the square roots of the radii, or the cube roots of the powers 

 employed. 



This result is very important to vessels intended for long voyages, where the great 

 quantity of coals with which they are required to be laden, so much increases the im- 

 mersion of the paddles, that the engine is not able to exert more than two thirds or 

 three fourths of its full power. In such cases an increase of speed will be given, 

 amounting to nearly one mile an hour, by reducing the diameter of the wheel so as to 

 allow the engine to perform its full duty ; and at the same time the consumption of 

 fuel is but little increased, as is shown by Captain Austin's experiments on the Sala- 

 mander. 



8th. That an advantage would be derived from a wheel of large diameter, as far as 

 the immersion of the paddle produced by loading the vessel is concerned, as it would 

 not so sensibly affect the angle of inclination at which it entered the water. This, 

 however, cannot be attained advantageously with an engine of the same length of 

 stroke, because to allow it to make its full number of strokes with the large wheel 

 the size of the paddles must be diminished, which is a much greater evil than a wheel 

 of small diameter with large paddles. To have larger wheels, it is therefore either 

 necessary to have the engines made with longer strokes, or to have the paddle-wheel 

 on a different shaft, in order to diminish their speed. These are both practical incon- 



