48 Mr Russell on the Fallacies of the 



I shall now, then, proceed to shew that the pressure produced 

 by the crank is not a loss of dynamical force ; that, where the 

 apparent loss is greatest, there is no loss at all, and that at every 

 point, the effect produced is directly proportioned to the quan- 

 tity of steam producing it. 



Let it be recollected that at the two extremes of the line of 

 the centres, the greatest apparent loss of force takes place. 



But is it not seen that at this instant there is in reality no loss 

 at all, because there is no expansion of steam, no consumption 

 of the elements ? The supply has been closed, the communica- 

 tion with the boiler is cut off, the steam has done its work, and 

 only waits to be dismissed from the chamber, which it leaves 

 on the instant that the eductive valve is thrown open for egress, 

 and access is given to the fresh supply which is forcing its way 

 inwards to the other side of the piston. 



The entering steam finds the piston almost in contact with 

 that end of the cylinder at which it enters. It insinuates 

 itself into the vacant disk, and powerfully expanding swells 

 out its thickness, propelling the disk of the piston towards 

 the other end of the cylinder. At first its progress is but 

 slow ; it gradually accelerates till the piston reaches the 

 middle of the cylinder, when it moves with the full velocity 

 of the crank in the centre. But, as the motion of the piston 

 must altogether cease on arriving at the end of the cylinder, it 

 is pi'epared for this event in a manner most exquisitely beauti- 

 ful ; for, from the moment of reaching the point which is half 

 way from the end of its course, the piston begins to be retarded, 

 the steam expands more and more slowly, the final stoppage is 

 gradually prepared for, and at last the rectilineal motion having 

 dwindled to nothing by insensible shades, altogether ceases; 

 the steam has expanded by a continually diminishing movement 

 and now ceases to produce any effect, and is released from its 

 confinement. Such is the history of the elemental power in its 

 transit through th3 cylinder, first communicating motion to the 

 piston by gradually increasing increments, and then bringing 

 it to rest, by decrements of motion, in the inverse order. 



Let us now trace, with equal minuteness, the simultaneous 

 phenomena of the ])oint, which, by its connection with the pis- 

 ton, is carried round in the circumference of a circle, while its 



