Royal Irish Academy. 495 



land. A conjecture was proposed as to the possible occasion of such 

 a movement of water over the countiy. The limestone tract was evi- 

 dently formed under the sea. Its elevation may have been connect- 

 ed with the last great convulsion, which determined nearly the pre- 

 sent form of the surface. Great chsturbances are seen at Killiney, 

 the Scalp, &c., to have attended the appearance of the granite, and 

 even to have followed that period, affecting the granite itself. Many 

 parts of the Irish coasts present such abrupt terminations towards 

 the sea, as to indicate either a violent raising of the island from a 

 continuous tract at the bottom, or a sudden sinking of an extent of 

 dry land around the present surface. Either of these events would 

 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 accumulations 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 wluch no limestone rocks exist. It is 

 but justice to Professor 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 evi- 

 dences of a glacier having existed in any locality must be derived 

 from the existing form of the ground ; and that, therefore, no con- 

 siderable 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 interval, it was con- 

 tended, would not allow time for their formation and disappearance. 



A gradual change of the temperature of the whole northern hemi- 

 sphere would be at variance with the fact established by geologists, that 

 the heatof the earth's surface had been formerlymuch greater than now. 



Had the degree of cold necessary for the formation of glaciers been 

 owing to a greater elevation of this entire country, its sinking to its 

 present level must have been attended with convulsions and floods, 

 which could scarcely have failed to obliterate all vestiges of moraines. 



An objection, brought from the known change of temjierature in 

 Grreenland within modern times, was met by observing, that Green- 

 land in its best days was always a land of glaciers, in the extent of 

 which it is easy to suppose an occasional increase or diminution. 



The reading of a paper by the Rev. T. R. Robinson, D.D., " On 

 the Constant of Refraction, determined by Observations with the 

 Mural Circle of the Armagh Observatory," was commenced. 



A pajjcr by Dr. Andrews of Belfast, " On the Heat developed 

 2G2 



