Notices of Memoirs — Boulder-drift of North America. 127 



beds have tliinnod away boforo tlioy roach Flintshire," and that I 

 had reached the limestone proper, but as I descended the section 

 passing various sandstones intcrstratilicd with the limestones, and 

 finally found the mass of white and rod sandstones at its base, 

 resting upon what appears to bo the main body of the Carboniferous 

 limestone, my impression was altered, and the conclusion which, 

 after much careful deliberation, I have arrived at is this; that in the 

 southern half of their course, the whole of the beds between the 

 Carboniferous Limestone and the Coal Measures do, on the North 

 Wales Border, most nearly resemble the division of rocks elsewhere 

 known as the Millstone Grit, btit that in their northern portion, from 

 the base of the white beds at the top of the Mold section, they have 

 greater affinity with those described as the Yoredale series, with 

 rather more of a calcareous element in their composition than the 

 latter usually possess. I would therefore venture to suggest whether 

 the time has not come when the whole of the beds lying between the 

 Great Scar Limestone, and the Coal Measures, varying as they do in 

 different localities, presenting many features in common, passing 

 rapidly, as we have seen, in what I have called the North Wales 

 district, from sandstone to limestone, and contrariwise, ought not to be 

 united into one great group, with subdivisions according to locality 

 and condition. 



iTOTioiBS OIF nyniEi^vnoiias. 



L — The Gkeat Botjlber Dkiets of North America. 



AN Article on the " Eolations and Characters of Western Boulder 

 Drift," by E. Andrews, M.D., appeared in Silliman's American 

 Journal for September last, of which the following is a brief 

 abstract : — 



The original Boulder-clay is beyond all question a stratified 

 water-deposit. More than 2,000 miles of it have been exposed by 

 waves along the shores of the great lakes, and along more than fifty 

 railroads which have cut the hills in every direction. The meaning 

 of the facts cannot be mistaken, and the western geologists most 

 familiar with the sections have heen obliged to abandon the glacier 

 theory, and to admit the aqueous origin of the Boulder-clay under a 

 sea floating vast quantities of ice. The original Boulder-clay is not 

 only clearly stratified and cross-stratified, but marked by a peculiar 

 style of undulation, and by the frequent occurrence of circular and 

 oval valleys without any outlet. The most remarkable facts are 

 those indicating the energy of the water during its deposition. As 

 first observed by Professor Jewell, of Chicago, in a long tunnel, it 

 contains two kinds of erratics, rocks and gravel-boulders, the latter 

 sometimes three feet in diameter. The gravel must have been dropt 

 from floating ice in frozen masses, and covered up before the masses 

 had time to melt. The clay therefore must have been deposited 

 with " unaccoimtable rapidity." 



Li Wisconsin, a remarkable valley, 400 miles long, runs mainly 



