92 Mr. J. Ball on the Formation of 



The vast moraines which circle round the openingof the greater 

 valleys on the southern side of the Alps, and extend beyond the 

 limits of the existing lakes, rest upon diluvium formed of the 

 same materials as the moraines, but extensively water-worn, the 

 pebbles being rounded and usually smaller in size, and the ma- 

 terials partially sifted and imperfectly stratified. The moraines 

 have evidently been left in their present position by the ancient 

 glaciers which filled up for a long period the lake-basins ; but 

 before the glaciers had filled these basins, how was the diluvium 

 carried across such long and deep hollows as those occupied by 

 the great Italian lakes ? M. Mortillet argues, with apparent 

 justice, that in order to reach the plain it must have first filled 

 up the intervening hollows. The conclusion does not, however, 

 seem to me necessary; and I will venture to suggest two alter- 

 natives, either or both of which in succession seem to me more 

 satisfactory. 



It is quite certain that during the period when the diluvium 

 was being reduced to its present condition, and was spread out 

 over the valley of the Po and the plain of Friuli, that tract was 

 the bed of a shallow sea ; and there is good reason to suspect 

 many oscillations of level between the meiocene period and the 

 last great extension of the glaciers, during which the region in 

 question may have been alternately uplifted and submerged. 

 Geologists who have renounced the doctrines of the cataclysmal 

 school have yet retained much of the language and habits of 

 thought which were there learned. It is still their tendency to 

 speak and think as if the history of the earth were that of a 

 series of great events (revolutionary periods) separated by in- 

 tervals of repose, rather than a slowly rolling cycle of incessant 

 change wherein the same natural agents, perhaps in altered 

 combinations and with varying intensity, constantly recur. 

 Since the importance of ice as an agent in geological change 

 has been clearly demonstrated, geologists have concentrated 

 their thoughts upon a single period immediately preceding the 

 establishment and actual distribution of the present fauna and 

 flora, and have, in accordance with their habitual tendency, called 

 this the glacial epoch. I am of course aware that some geolo- 

 gists have pointed out the traces of glacial action at former 

 geological periods ; but it cannot be said that they have generally 

 recognized the reasonable conclusion, that if one of the latest 

 conditions of the earth admitted of a great extension of glacial 

 action, a similar combination of causes must probably have 

 brought about the same effects at many recurring periods. 



To my mind there is nothing strange in the supposition that 

 the materials of the diluvium of the valley of the Po were 

 brought down from the upper valleys of the Alps and across the 



