OF NATURAL PHILOSOPHY. 147 



and sea over the surface of the globe : a change of 

 such distribution, in the lapse of ages, by the degra- 

 dation of the old continents, and the elevation of 

 new, being a demonstrated fact ; and the influence 

 of such a change on the climates of particular re- 

 gions, if not of the whole globe, being a perfectly 

 fair conclusion, from what we know of continental, 

 insular, and oceanic climates by actual observation. 

 Here, then, we have, at least, a cause on which a 

 philosopher may consent to reason; though, whether 

 W the changes actually going on are such as to warrant 

 the whole extent of the conclusion, or are even 

 taking place in the right direction, may be con 

 sidered as undecided till the matter has been more 

 thoroughly examined. 



(140.) To this we may add another, which 

 has likewise the essential characters of a vera 

 causa, in the astronomical fact of the actual slow 

 diminution of the eccentricity of the earth's orbit 

 round the sun ; and which, as a general one, affect- 

 ing the mean temperature of the whole globe> and 

 as one of which the effect is both inevitable, and 

 susceptible, to a certain degree, of exact estimation, 

 deserves consideration. It is evident that the 

 mean temperature of the whole surface of the 

 globe, in so far as it is maintained by the action 

 of the sun at a higher degree than it would have 

 were the sun extinguished, must depend on the 

 mean quantity of the sun's rays which it receives, or, 

 which comes to the same thing, on the total quantity 

 received in a given invariable time : and the length 

 of the year being unchangeable in all the fluctu- 

 ations of the planetary system, it follows, that the 

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