Northern Erratics. 101 



question, as the northern erratics occur here in an undis- 

 turbed continuation over tracts of land far more extensive 

 than those in which they have been observed in Europe. 

 For my own part, I have already traced them from the eastern 

 shores of Nova Scotia, through New England and the north- 

 western States of North America and the Canadas as far as 

 the western extremity of Lake Superior, a region embracing 

 about thirty degrees of longitude. Here, as in Northern 

 Europe, the boulders evidently originated farther north than 

 their present location, and have been moved universally in a 

 main direction from south to north. 



From data which are, however, rather incomplete, it can 

 be further admitted that similar phenomena occur further 

 west across the whole continent, everywhere presenting the 

 same relations. That is to say, everywhere pointing to the 

 north as to the region of the boulders, which generally dis- 

 appear about latitude 38°. 



Without entering at present into a full discussion of any 

 theoretical views of the subject, it is plain that any theory, 

 to be satisfactory, should embrace both the extensive northern 

 phenomena in Europe and North America, and settle the 

 relation of these phenomena to the well-authenticated local 

 phenomena of Central Europe. 



Whether America itself has its special local circumscribed 

 centres of distribution or not, remains to be seen. It seems, 

 however, from a few facts observed in the White Mountains, 

 that this chain, as well as the mountains of north-eastern 

 New York, have not been exclusively, — and for the whole 

 duration of the transportation of these materials, — under the 

 influence of the cause which has distributed the erratics 

 through such wide space over the continent of North Ame- 

 rica. But, whether this be the case or not (and I trust local 

 investigations will soon settle the question), I maintain that 

 the cause which has transported these boulders in the Ame- 

 rican continent, must have acted simultaneously over the 

 whole ground which these boulders cover, as they present 

 throughout the continent an uninterrupted sheet of loose 

 materials, of the same general nature, connected in the same 

 general manner, and evidently dispersed at the same time. 



