39 



Either of these events \rould create immense commotions in 

 the waters. 



Reference was made, in the course of this argument, to 

 the theory of Professor Agassiz, respecting the supposed 

 evidence, that glaciers once existed in the mountains of this 

 island, and produced, as moraines, some of the accumula- 

 tions of mountain debris commonly attributed to the agency 

 of water. This theory having been pushed so far by some 

 eminent British geologists as to have almost every ridge of 

 gravel and stones unhesitatingly called a moraine, it was 

 urged, that their principle could not be applied here at least, 

 since the limestone abounding in the deposits of the glens 

 could never have been brought down by ice from mountains 

 in which no limestone rocks exist. It is but justice to Pro- 

 fessor Agassiz to state, that he did not ascribe the limestone 

 gravel ridges at Ballynascorney to a glacier ; but professed 

 to find the traces of one higher up the course of the stream. 



Against the glacier theory, in general, it was maintained, 

 that evidences of a glacier having existed in any locality 

 must be derived from the existing form of the ground ; and 

 that, therefore, no considerable change of the surface could 

 be admitted, since the time when the moraines were 

 imagined to have been thrown up. More especially, no 

 deluge could have taken place since their formation ; for in 

 that case, the moraines must have been swept away. Hence 

 they must be supposed to have existed between Noah's flood 

 and the commencement of the historical periods. This inter- 

 val, it was contended, would not allow time for their forma- 

 tion and disappearance. 



A gradual change of the temperature of the whole nor- 

 thern hemisphere would be at variance with the fact esta- 

 bhshed by geologists, that the heat of the earth's surface had 

 been formerly much greater than now. 



Had the degree of cold necessary for the formation of 

 glaciers, been owing to a greaterelevation of this entire coun- 



