146 Geological Society. Mr. Lyell on the 



to the latter epoch, therefore, that we ought to refer the inclined 

 heaches observed in Norway by M. Bravais. 



The fact that the post- tertiary sea-beaches are, in the great ma- 

 jority of instances, horizontal, strongly militates against the notion 

 that they owe their present position to elevation from beneath ; as 

 does also the fact of their wide-spread geographical distribution, 

 which is so extensive indeed as to be almost universal. Were we to 

 admit that wherever these beaches are found the land has been ele- 

 vated, we must admit that in the post-tertiary period the elevating 

 of the land was almost universal ; a conclusion in itself so impro- 

 bable, that we ought to seek to explain the difference of level between 

 the post-tertiarv beaches and the present ocean in some other manner. 



The author then propounds a new theory to account for the post- 

 tertiary horizontal sea-beaches. This theory he bases on the above 

 stated conclusion, derived from the appearances which the diluvium 

 and the alpine boulders present ; namely, that during the post-ter- 

 tiary period the temperature of the earth was lower than it is at pre- 

 sent. From the observations of Kotzebue, Sabine and Scoresby, he 

 infers, that at the depth of about 800 fathoms from the surface the 

 temperature of sea water, whether near the equator or in high 

 latitudes, is not very remote from 40 degrees of Fahrenheit, the point 

 of temperature at which the density of fresh water is the greatest : 

 and as the mean depth, according to Laplace, of the Pacific Ocean 

 is about four miles, and of the Atlantic about three miles, and the 

 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 sea water 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 temperature 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 

 po#t-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. 



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

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



May 10, 1843. — "On the Coal-formation of Nova Scotia, and on 

 the age and relative position of the Gypsum and accompanying 

 marine limestones." By Charles Lyell, Esq., F.G.S.. tic. 



