82 CORRELATION OF PHYSICAL FORCES. 



ity, but that some may be increasing, others dwindling away, 

 and so throughout the universe, in the past as in the future. 

 When, however, questions relating to cosmogony, or to the 

 beginning or end of worlds, are contemplated from a physi- 

 cal point of view, the period of time over which our experi- 

 ence, in its most enlarged sense, extends, is so indefinitely 

 minute with reference to that which must be required for any 

 notable change, even in our own planet, that a variety of the- 

 ories may be framed equally incapable of proof or of dis- 

 proof. We have no means of ascertaining whether many 

 changes, which endure in the same direction for a term be- 

 yond the range of human experience, are really continuous or 

 only secular variations, which may be compensated for at 

 periods far beyond our ken, so that in such cases the ques- 

 tion of comparative stability or change can at best be only 

 answered as to a term which, though enormous with refer- 

 ference to our computations, sinks into nothing with reference 

 to cosmical time, if cosmical time be not eternity. Subjects 

 such as these, though of a kind on which the mind delights 

 to speculate, appear, with reference to any hope of attaining 

 reliable knowledge, far beyond the reach of any present or 

 immediately prospective capacity of man. 



