OF NATURAL PHILOSOPHY. 41 



may be, they must fall somewhere, and continue, 

 if only as ingredients of the soil, to perform their 

 humble but useful part in the economy of nature. 

 The destruction produced by fire is more striking : 

 in many cases, as in the burning of a piece of 

 charcoal or a taper, there is no smoke, nothing 

 visibly dissipated and carried away; the burning 

 body wastes and disappears, while nothing seems to 

 be produced but warmth and light, which we are 

 not in the habit of considering as substances ; and 

 when all has disappeared, except perhaps some 

 trifling ashes, we naturally enough suppose it is 

 gone, lost, destroyed. But when the question is 

 examined more exactly, we detect, in the invisible 

 stream of heated air which ascends from the glow- 

 ing coal or flaming wax, the whole ponderable matter, 

 only united in a new combination with the air, 

 and dissolved in it. Yet, so far from being thereby 

 destroyed, it is only become again what it was 

 before it existed in the form of charcoal or wax, an 

 active agent in the business of the world, and a 

 main support of vegetable and animal life, and is 

 still susceptible of running again and again the same 

 round, as circumstances may determine ; so that, 

 for aught we can see to the contrary, the same 

 identical atom may lie concealed for thousands of 

 centuries in a limestone rock; may at length be 

 quarried, Set free in the limekiln, mix with the air, 

 be absorbed from it by plants, and, in succession, 

 become a part of the frames of myriads of living 

 beings, till some concurrence of events consigns it 

 once more to a long repose, which, however, no way 

 unfits it from again resuming its former activity. 



