330 MR. P. W. BARLOW ON THE LAWS WHICH GOVERN 



2444 horses, which would g-ive a still less fraction than a fifteenth ; but compared 

 with a cylinder with flat ends, the number of horse powers is 2275, and the fraction 

 greater than -Vth, but less than ^th, a confirmation which I could have scarcely 



hoped to have obtained. 



These results are deduced as below. According to Colonel Beaufoy's experiments, 

 Table I. Part III., it requires a force of 203*79 pounds to urge a plane of one square 

 foot through still water at the rate of eight nautical miles per hour, or 810 feet per 

 minute: now the Medea moved with a velocity of 11*33 miles per hour, or 966 feet 

 per minute ; it would therefore require, according to Colonel Beaufoy^ (the resistance 

 being as the square of the velocity,) 



8102 : 9962 . 203*79 lbs. : 308 lbs. 

 Now the section being 263 feet, the resistance per foot 308 pounds, and the velocity 



996 feet per minute, 



308 X 996 X 263 _ 



33000 ~ ^444, 



the number of horse power requisite to urge a plane section of this area at the given 

 rate. But if instead of a mere plane we take Colonel Beaufoy's experiments for a 

 cylinder with flat ends, which required only 190*78 pounds, we obtain the number of 

 horse power 2275 as above stated. 



If I had made use of the results of Colonel Beaufoy's experiments throughout the 

 preceding investigations, the numbers in Column ] 7 of Table II. and in Column 4 of 

 Table V. would have been increased by about one seventh ; and in estimating the 

 power exerted on the paddles, it would have been found to exceed the nominal power 

 of the engine, which proves that engines work above their nominal power. 



General Deductions from the preceding Investigations. 



On a general examination of the preceding results, I am led to the following con- 

 clusions. 



1st. That when the vessels are so laden that the wheel is but slightly immersed, 

 there is little advantage in the vertically acting paddle. 



2nd. That in cases of deep immersion it has considerable advantage over the com- 

 mon wheel as at present constructed. It has an advantage, in consequence, in a sea 

 where the degree of immersion is continually varying. 



3rd. That in the common wheel, while the paddle passes the lower part of the arc, 

 or when its position is vertical, it not only affords less resistance to the engine, but is 

 less effective in propelling the vessel than in any part of its revolution. 



4th. That in the new wheel the paddle while passing the lower part of the arc af- 

 fords more resistance to the engine, and is more effective in propelling the vessel, 

 than in any part of its revolution. 



This property of the vertical paddle is a serious deduction from the value of the 



