50 Mr Russell on the Fallacies of the 



thetical case of uniform reciprocating motion in the piston ; so 

 that the piston, when elevated and depressed by the steam, draws 

 the crank down with it from A to B and C, and raises it up 

 with it from C to D and A. Let the orbit of the crank be di- 

 vided into twenty equal parts, the first ten numerals being 

 placed on the descending side, and the other ten on the ascend- 

 ing side of the circle. Let the length of the stroke of the pis- 

 ton, which is equal to the diameter of the circle, be divided 

 into ten parts, shewing the place of the piston at every instant 

 of its stroke, contemporaneous with the points of the crank in 

 its orbit ; the first ten numerals corresponding both in the 

 circle and the cylinder with corresponding points of reciproca- 

 tion and of revolution. 



Now, at each of these points, let us examine into the relation 

 which exists between the pressure of the steam on the piston 

 And the quantity of the effect produced in revolving the crank, 

 and that part of the pressure of the steam which produces no 

 motion, and which is therefore erroneously said to be lost. The 

 jjressure of the steam acting obliquely on the crank produces 

 two effects ; — pressure towai'ds the centre through the crank, 

 and motion in the direction of the circle tangentically. See 

 Y\g%. 7 and 8, in which the arrows placed as tangents repre- 

 Fig. 7. Fig. 8. 



^4^ 



sent effective rotating force, the vertical lines the power of the 

 steam, and the lines directed to the centre the apparent loss. 

 Let the whole pn.ssure of the steam be taken at 100 lb., then, 

 by ascertaining the proportion which the lines a, b, and c, in the 

 direction of those parts bear to each other, it will be seen that, 

 at the first division, the force in the direction of the circle is 

 only 31 per cent, of the force on the piston ; at the second 

 division it will be found to amount to (58.78) 59 per cent ; 

 at the third to (80.90) 81 per cent. ; at the fourth to (95.11) 



