324 



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



of, the radius rod. The effect to turn the line A B about the point A will be the force 

 H B alone ; the force G H, which is in the direction of the line A B, having no power 

 to turn it, its whole action being on the axle of the wheel. It therefore follows, 

 that the force F B at right angles to the radius rod required to retain the point B in 

 equilibrio, or to exert a force in a horizontal direction equal to GB, is GB cos (p, be- 

 cause the angle G B H = B A I, and consequently equal to (V cos <p — vY cos <p, as 

 already stated in a preceding page. 



Having assumed in this case the same angle of 44° when the paddles begin to act, 

 I find the mean of the horizontal resistances on the paddle from the equation 

 (V cos <p -- vY to be -547, and the mean of the forces necessary to balance these 

 resistances from the equation (V cos <p — vY cos <p to be -522 (the force on the lower 

 paddle being 1), which multiplied by 2|, the number of paddles acting, makes the 

 whole power of the engine employed on the paddles to be 1*436 times that exerted on 

 the vertical paddle, or the proportion of the power of the engine employed on the 

 lower paddle to be '696 ; the mean given by the experiments being '546. There is, 

 therefore, a deficiency of '150 of the power of the engine to account for, which I sup- 

 pose partly due to the friction of the wheel, and partly to the deviations of the paddle 

 from the vertical position, which, as before observed, results from the construction. 



Consumption of Coals at different speeds. 



It may be seen by referring to our first Table of experiments, that in deeply laden 

 vessels the engines make little more than two thirds of the number of strokes due to 

 their full power. Now if this number of strokes required only two thirds the steam 

 necessary to keep the engine in full action, the loss sustained in deeply laden vessels 

 would be simply that due to the oblique action of the wheel ; but unfortunately nearly 

 as much steam and as much fuel are required in these oases to procure fifteen strokes, 

 as to make the engine perform its full number of twenty-two strokes under other cir- 

 cumstances. To verify this assertion, which is perhaps a very unexpected one, to those 

 who are not intimately acquainted with the navigation of steam vessels in long 

 voyages, I give the following Table, kindly supplied me by Captain Austin, R.N., the 

 observations having been made by his order and under his own superintendence whilst 

 in command of His Majesty's steamer Salamander. By a reference to this Table it 

 will be seen that there is no proportional relation between the speed of the vessel, or 

 even the speed of the piston, and the consumption of fuel, which may be accounted 

 for in a great measure by the loss of lieat from the radiation being constant at all 

 velocities ; but from whatever cause it proceeds, it is obviously an object of the 

 greatest importance to the progress of improvement of steam navigation, that some 

 means should be found of enabling an engine to perform its full duty under all de- 

 grees of immersion. When a vessel commences a long voyage she is necessarily 

 deeply immersed, and at the end of it, her fuel being consumed, her paddles are not 

 perhaps immersed so deeply by nearly three feet. In the latter case the effective part 

 of the power exerted is -660, and the power exerted is the whole power of the engine; 



