INTR OD UCTOR Y REMARKS. 1 3 



on the glass ; while this is in the state of tension, the force is 

 ever existing, capable of reproducing the original motion, and 

 while in a state of abeyance as to actual motion, it is really 

 acting on the glass. The motion is suspended, but the force 

 is not annihilated. 



But it may be objected, if tension or static force be thus 

 motion in abeyance, there is at all times a large amount of 

 dynamical action subtracted from the universe. Every stone 

 raised and left upon a hill, every spring that is bent, and has 

 required force to upraise or bend it, has for a time, and pos- 

 sibly for ever, withdrawn this force, and annihilated it. Not 

 so ; when we raise a weight and leave it at the point to which 

 it has been elevated we have changed the centre of gravity of 

 the earth, and consequently the earth's position with reference 

 to the sun, planets, and stars ; the effort we have made per- 

 vades and shakes the universe ; nor can we present to the 

 mind any exercise of force, which is not thus permanent in its 

 dynamical effects. If, instead of one weight being raised, we 

 raise two weights, each placed at points of the earth diame- 

 trically opposite each other, it would be said, here you have 

 compensation, a balance, no change in the centre of gravity of 

 the earth ; but we have increased the mean diameter of the 

 earth, and a perturbation of our planet, and of all other celes- 

 tial bodies, necessarily ensues. 



The force may be said to be in abeyance with reference to 

 the effect it would have produced, if not arrested, or placed in 

 a state of tension ; but in the act of imposing this state, the 

 relations of equilibrium with other bodies have been changed, 

 and these move in their turn, so that motion of the same 

 amount would seem to be ever affecting matter conceived in 

 its totality. 



Press the hands violently together ; the first notion may 

 be that this is power locked up, and that no change ensues. 

 Not so ; the blood courses more quickly, respiration is acce- 

 lerated, changes, which we may not be able to trace, take 

 place in the muscles and nerves, transpiration is increased ; we 

 have given off force in various ways, and must, if such efforts 

 be prolonged, replenish our sources of power, by fresh chemical 

 action in the stomach. 



