138 R. Pumpelly—Secular Rock-disintegration. 
considerably farther northward than that at the bottom. = 
can only thus account for the disappearance of the vast ee 
of residuary disintegrated material that must have existed 0V : 
the surface of the Archean feldspathic rocks of eastern Bri 
America. But in Northern Asia, north of the 40th degree - 
latitude there are no traces of a general glacial action such 
existed in Northeastern America and Northern Europe. 
a verbal communication of Professor W. B. Rogers, ag 
ecay is general throughout the schists of the Southeastern 
where its depth often exceeds two hundred feet. : me 
ander Agassiz and Mr. Thomas MacFarlane have both informed “ 
ce this paper was written, I have had occas : alia 
extent of the disintegration in place that exists in the slates, diorites and sye™ 
granites of the foot-hills of the Sierra Nevada in California. 
