306 Scientific Proceedings, Royal Dublin Society. 



buting to all a common origin and the same horizon, unless this 

 term be so indefinitely used as to dilute its value in a proportionate 

 degree. 



The systematic accumulation of further facts may confirm or 

 modify the now somewhat speculative ideas put forward regarding 

 this palaeozoic ice age, still the balance of evidence is at present in 

 its favour, and we should bear in mind that if one glacial period 

 be taken as established, another may also have prevailed upon the 

 earth in other and remoter times. 



I have thus endeavoured to bring to your notice, as briefly as 

 possible, two out of the many subjects which have recently engaged 

 the attention of geologists — two subjects which appear to possess 

 more than ordinary interest. And, in conclusion, I would ask you 

 to gather from their consideration elsewhere that, as the years of 

 our science increase and its votaries multiply, the expanding field 

 of its investigations becomes ever a land of promise wherein the 

 realization of things undreamt of in the philosophy of our fathers 

 will still reward the search of those who labour to complete the 

 history of the earth. 



NOTE ADDED IN THE PEESS. 



Since the above was written information has been received that 

 Trilobites have been discovered in the Obolus zone of the Salt 

 Range, and that these Trilobites are supposed by Dr. Waagen 

 to be of Cambrian age. This would materially alter the views 

 already published as to the Silurian, or, as Dr. Waagen subse- 

 quently suggested, Carboniferous age to which this fossiliferous 

 zone might be referred. — 16th March, 1889. 



