THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOUENAL OF SCIENCE. 



[FOURTH SERIES.] 



APRIL 1865. 



XXXVI. On the Application of the Principle of the Screw to the 

 Floats of Paddle-wheels. By W. G. Adams, M.A., F.G.S., 



Fellow of St. John's College, Cambridge, Lecturer on Natural 

 Philosophy at King's College, London*. 



THE following calculation is an attempt to apply the mathe- 

 matical laws of fluid-motion, "as far as they may be de- 

 pended on, to an important practical question with regard to 

 paddle-wheel steamers, viz. the comparison of the pressure of a 

 fluid on a float in the form of the surface of a screw, with the 

 pressure on the ordinary flat float, so as to discover whether any 

 advantage would be gained by having the floats of paddle-wheels 

 made in the form of a screw-surface. This application of the prin- 

 ciple of the screw has been conceived by Dr. Croft of St. John's 

 Wood, who has tested it by means of small working models 

 with very satisfactory results, both as to the speed when the boat 

 is either lightly or heavily laden, and also as to the steadiness of the 

 pulling power. In all cases on the small boat, the new is 

 superior to the old paddle-wheel when they are of the same dia- 

 meter, and even when the new wheel is narrower than the old 

 one. It has also been tried on larger boats, and the two kinds 

 of floats have been compared; and the results have been in 

 favour of the new principle, there being no large waves or 

 strong backward current in the case of the new wheel, and the 

 velocity and steadiness of motion being greater than in the 

 paddle-wheel with flat floats. This principle is now being 

 applied, under Dr. Croft's directions, to one of Her Majesty's 

 steamers. 



Suppose A B (fig. 2) to be the axis of the paddle-wheel, and A G 



* Communicated by the Author. 

 Phil Mag. S. 4. Vol. 29. No. 196. April 1865. S 



