374 I. C. White — Bowlders at high altitudes. 



has progressed upwardly to irregular distances among the early 

 fragmentals, we should be calling fragmental rocks of one 

 region Agnotozoic, while the crystalline schists, representative 

 of these in other regions, would be classed as Archasan. In 

 reply to this objection I should say, in the first place, that a 

 number of the geologists who of later years have concerned 

 themselves with the early formations have been tending more 

 and more to the conclusion that there is always a reasonably 

 easy line of demarkation between the true Archasan crystallines 

 and the overlying fragmentals. My own experience has led 

 me strongly toward such a view. But even if this be not the 

 case, it is to be said that the lower limit of the proposed 

 Agnotozoic would on the whole be but little more arbitrary in 

 any universal application than are those lines generally ac- 

 cepted as established paleontologically. These paleontological 

 boundaries have generally been established in the first place 

 for a restricted region, and their application to other geological 

 basins, and particularly to distant continents, has always been 

 in a measure an arbitrary one. It should be understood dis- 

 tinctly that the term is proposed to cover, not any non-fossilifer- 

 ous formations lying beneath the Cambrian — since so far as 

 they are in complete conformity with the overlying Cambrian 

 they may be merely its downward extensions — but such non- 

 fossiliferous and distinctly fragmental and sedimentary rocks as 

 are separated from the Cambrian base by a genuine wide-spread 

 unconformity ; that is, by a structural break indicative of an 

 enormous lapse of unrecorded time. 



Aet. XL. — Rounded Bowlders at high altitudes along some 

 Appalachian Rivers ; by I. C. White. 



In a paper read at the Minneapolis meeting of the American 

 Association the writer described some deposits along the Monon- 

 gahela and Teazes valleys in West Virginia, that seemed to 

 furnish strong confirmation of Professor Wright's hypothetical 

 ice dam. Since the preparation of that paper many other facts 

 bearing on the question at issue have come under my observa- 

 tion, and they are here placed on record with a view of assist- 

 ing those who are making a specialty of surface geology to the 

 correct solution of the problems they involve. 



That the terrace deposits along the Monongahela, Allegheny 

 and Ohio valleys were formed during a submergence of some 

 kind, will, I think, hardly be questioned by anj^ geologist 

 thoroughly familiar with the nature and extent of the deposits 

 themselves: for there are numerous localities where the evi- 



