and its Influence on Climate. 443 



For a few thousand years before and after 11,700 years ago, 

 when the winter solstice was evidently not far from aphe- 

 lion, and the sea standing considerably above its present level, 

 would probably, as we have already stated, be the time when the 

 Carse clays, the stratified sand and mud which form our Glas- 

 gow Green, and other recent deposits lying above the present 

 level of the river, were formed. And it is also a singular fact 

 that the condition of things at this period must have been ex- 

 ceedingly favourable to the formation of such estuarine de- 

 posits ; for at this time the winter temperature of our island, 

 as has been already shown, would be a few degrees below the 

 freezing-point, and consequently during that season snow would 

 fall instead of rain. The melting of the winter's accumulation 

 of snow on the approach of summer would necessarily produce 

 great floods, similar to what occur in the northern parts of 

 Asia and America at the present day from this very same cause. 

 The loose upper soil would be carried down by those floods and 

 deposited in the estuaries of our rivers. 



The foregoing is a rough and imperfect sketch of the history 

 of the climate and physical conditions of our globe for the past 

 60,000 years, so far as physical and cosmical considerations 

 seem to afford us information on the subject ; and its striking- 

 agreement with that derived from geological sources is an ad- 

 ditional evidence in favour of the opinion that geological and 

 cosmical phenomena are physically related by a bond of cau- 

 sation. 



We have assumed 1° 22' 34" greater than the present obli- 

 quity as the maximum. But this limit assigned by Laplace 

 does not hold true for all time past *. And Sir John Herschel 

 thinks that when millions of years are taken into account, the 

 obliquity may even amount to 3° or 4° on each side of a mean 

 state fi 



Suppose, then, that at some past geological epoch the in- 

 crease of the obliquity reached 4°, the equator would then be 

 receiving 5*64 thermal days less heat than at present, and the 

 poles upwards of 24 thermal days more heat than at present. 

 The total quantity of heat received by the poles would therefore 

 be nearly ^ more than at the present day. For every 6 pounds 

 of ice now melted at the pole, 7 pounds would then be melted. 

 Were this condition of things to occur when the excentricity 

 was near its superior limit, the hemisphere which had its winter 

 occurring in perihelion at the time, would in all probability be 

 completely deprived of its ice-cap, and forest-trees might then 

 grow at the pole. 



* Mecaiiique Celeste, vol. ii. p. 857, note, Bowditch's translation. 

 t Lyell's ' Principles/ new edition, vol. i. p. 282.J 



