XVII. — On the Astronomical Causes ichicli may influence Geological 



Phcenomena. 



By J. P. W. HERSCHEL, Esq. M.A. F.G.S. P.R.S. L. & E. 



CORRESPONDENT OF THE ROYAL ACADEMY OF SCIENCE OF PARIS^ &C. &C. 



[Read December 15, 1830.] 



Although the more immediate object of g-eologists in the actual state of 

 their science is rather the collection of facts^ and such an induction of con- 

 clusions from them as shall be, so far as possible, independent of theory ; yet 

 when theory confines itself to pointing out the influence of causes which we 

 know to exist, in modifying- the general condition of our globe, and enables 

 us to estimate the extent of their action, it may be regarded as rendering a 

 real service to science. It thus tends in some degree to diminish the com- 

 plexity of the problems to be resolved, or at least to reduce them to their true 

 difficulty, by showing what portion of them can and what cannot be accounted 

 for on known principles, thereby narrowing the field of research, and direct- 

 ing the efforts of future speculators to the discovery of causes of another de- 

 scription. 



This consideration has induced me, not without some degree of hesitation, 

 to offer to this Society, though in a very crude and imperfect state, some views 

 which have occurred to me of a possible explanation of a portion, at least, of 

 that great geological phaenomenon, — the difference between the actual climates 

 now prevailing over extensive regions of the earth's surface, and perhaps over 

 its whole extent, and those which the organic remains discovered in its strata 

 lead us to conclude have formerly subsisted during very long periods of time. 

 The ingenious attempts which have been lately made to account for this 

 remarkable fact, while they show the sense of geologists of the importance of 

 the subject, seem to indicate an impression that it is one on which we need 

 not despair of coming to just conclusions, and that in consequence no inquiry 

 will be considered as irrelevant which has for its object to bring into view the 

 action of causes which demonstrably must have an influence, and respecting 

 which the only question is its amount. 



Impressed with the magnificence of that view of geological revolutions 



