144 M. Desor on 



diluvium, would seem to prove that the period could not have 

 been long. Nowhere are the grooves and scratches more 

 distinct, than where they have been uncovered by removing 

 the diluvium ; they usually form a striking contrast with those 

 rounded rocks, whose surface has been for a long time exposed 

 to the wearing effects of the atmosphere.* But as we have no 

 reason to suppose that the action of the atmospheric agents 

 was formerly less energetic than now, I am compelled to be- 

 lieve that the preservation of the polished surfaces under the 

 diluvium, is owing to their having been exposed only a com- 

 paratively short time to wear from these agents. It is even 

 probable that the invasion of the sea was one of the causes 

 which have been active, if not decisive, in the destruction of 

 the great glaciers. It explains, at the same time, the colder 

 character of the diluvial fauna ; for a mass of ice so con- 

 siderable could not be melted without materially chilling 

 the waters which bathed it. The cold having slowly disap- 

 peared, the temperature would have been gradually elevated, 

 and the fauna of the waters would take by degrees the more 

 temperate character which distinguishes it at the present 

 day. 



To this epoch of the invasion of Scandinavia by the waters 

 of the sea, we should refer the arrangement in beds of the 

 mud, sand, and gravel, which the great glacier has left in 

 place, in testimony of its ancient extent. The action of waves 

 coming in upon this moveable soil, has here overturned and 

 heaped up the debris of marine life upon the shore, where 

 the remains are found mingled with scratched rocks and peb- 

 bles. If such is really the origin of these deposits, there is 

 no reason for surprise that the scratched pebbles should be 

 so numerous. The waves, in striking them against each 

 other, would wear them more or less ; and if blocks of a con- 

 siderable size have generally better preserved their markings 



* We may believe, that if, after a new deluge, the boulders which are at 

 present exposed, should be covered again with gravel, the geologists of future 

 ages would have much more trouble in ascertaining the causes which have i)ro- 

 duced the eflfects, than we have at the present day, aided as we are by the pre- 

 sorvations, frequently admirable, of the polishing, furrows, and fine strife. 



