136 APPENDIX. 



whence the horizontal or effective pressure is equal to 



7T 2 2 bfw 



900 x2 -P cos - * cos - 



the mean value of which is 



7T W 2 b fw C r 



900 x 2g o > 



or, 



> *' + 2 * + * cos " f 2 - 3 



The mean effective pressure on the two wheels, which is equal to the resistance opposed to 

 the motion of the vessel, is therefore 

 tr w 2 bfwm ( 



COS< f ~ 



I * 



Multiplying this by -^r-j the velocity of the vessel in feet per second, we find the pro- 

 oU 



pelling power in Ifes. moved through one foot in a second to be equal to 



COS< f2 ~ 



2 



which, reduced to horse powers, becomes 

 Tr 2 n 3 b fw m o 



22275000 x2ff < ~ > ~ = H - P - E ..... (4) 



The first member of this equation being equal to the second member of the equation (2) 

 (page 127), the sum of the terms between the brackets in the former, multiplied by If, is 

 equal to the sum of the terms between brackets in the latter ; or, calling S' that sum in the 

 equation (2), and S'" that in the equation (4), we have 



Q'" _ ^' 



' 2?' 



The following tables were constructed, like the two former, by assuming values for z until 

 the equations (2) and (4) gave the same value of S'". 



