ON THE GENERAL THEORY OF THE STEAM ENGINE. 



Values of z* 



199 



In the foregoing example we have x = - - = 0'8 ; immersion = 0*47 ; hence z = 0*74, and 



proportion of power effective = x z = 0*59. In this way a tolerably good estimation of the 

 relative effect of a wheel can be made almost at sight. 



2. VERTICALLY ACTING WHEEL. 



Take the hypothetical case worked by Mr. Mornay, at page 151, for the vertically acting 

 paddles, and suppose the centre of pressure to be in the middle of each paddle, which is 

 always nearly the case when the velocity of the paddle bears a high proportion with that of 

 the vessel. 



First, to calculate the requisite quantity of PADDLE SURFACE (S) we have a = 5, k = 9'25, 

 n = 30-439, speed of the vessel = 8'15 miles per hour, and the effective horse power = 88'33 ; 

 hence, 



Effective Power 88-33 log. 1-94611 

 2-5090 0-39950 



2-5090 



log. 1-54661 



S . . 35 "205 square feet of paddle surface. 



