CONCLUDING REMARKS. 175 



suspension ; this force, though ever existent, can never be 

 restored in its integrity to the ball of the pendulum, for in 

 the process of restoration it must affect other matter, and 

 alter the condition of the universe. To restore the initial 

 force in its integrity, everything as it existed at the moment 

 of the first beat of the pendulum must be restored in its 

 integrity; but how can this be? for while the force was 

 escaping from the pendulum by radiating heat from the point 

 of suspension, surrounding matter has not stood still ; the 

 very attraction which caused the beat of the pendulum has 

 changed in degree, for the pendulum is nearer to or farther 

 from the sun, or from some planet or fixed star. 



It might be an interesting and not profitless speculation 

 to follow out as far as may be these and other consequences : 

 it would, I believe, lead us to the conviction that the universe 

 is ever changing, and that, notwithstanding secular recurrences 

 which would, primd facie, seem to replace matter in its original 

 position, nothing, in fact, ever returns or can return to a state 

 of existence identical with a previous state. But the field of 

 enquiry is illimitable. 



The inevitable dissipation or throwing off a portion of the 

 initial force presents a great experimental difficulty in the 

 way of establishing the equivalents of the various natural 

 forces. In the steam-engine, for instance, the heat of the 

 furnace not only expands the water and thereby produces 

 the motion of the piston, but it also expands the iron of the 

 boiler of the cylinder and all surrounding bodies. The force 

 expended in expanding this iron to a very small extent is 

 equal to that which expands the vapour to a very large 

 extent : this expansion of the iron is capable, in its turn, of 

 producing a great mechanical force, which is practically lost. 

 Could all the force be applied to the vapour, an enormous 

 addition of power would be gained for the same expenditure ; 

 and perhaps, even with our present means, more might be 

 done in utilising the expansion of the iron. 



Another great difficulty in experimentally ascertaining the 

 dynamic equivalents of different forces arises from the effects 

 of disruption, elongation, or the overcoming an existing force. 

 Thus, when a part of the initial force employed is engaged in 



