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mean depth, therefore, of the two oceans about 3000 fathoms (of 

 •which 800 fathoms is little more than a fourth part), he considers 

 that the mean temperature of the whole of the seawater taken to- 

 gether, is not far remote from 40 degrees. He infers from the ob- 

 servations made by Captain Sabine on sea water in high latitudes, 

 that sea water follows nearly the same law as fresh water in expand- 

 ing with a reduction of temiserature below 40 degrees of Fahrenheit. 

 Hence he reasons, that if, during the post-tertiary period, the mean 

 temperature of the earth was lower, the mean temperature of the 

 sea was also lower than it is at present ; and this reduced tempera- 

 ture of the sea below 40 degrees would cause it to occupy a greater 

 volume than it now occupies, and consequently to rise on all the 

 sea coasts to a higher mean level than it now rises ; though not 

 exactly in proportion to its expansion, since it would then not only 

 be deeper but would occupy a greater surface than before. 



The author seeks to account for the increase which he supposes 

 to have taken place in the mean temperature of the earth since the 

 post-tertiary period, by the extent of land within the tropics which 

 since that period has been raised from beneath the ocean by subter- 

 ranean agency, and which, since its upheaval, has been heated by 

 the sun's rays. 



He notices the fact, that in the south-west of Lancashire the dilu- 

 vium is found resting only upon level, and not on inclined surfaces. 



