524 THE JOURNAL OF GEOLOGY. 



feet in the ice-sheet. 1 Probably some of the englacial drift there 

 was as high as 1,000 feet or more in the ice, but doubtless a 

 larger part was below than above the altitude of 500 feet ; and 

 this was on an area where the ice-sheet had attained probably a 

 thickness of 5,000 or 6,000 feet, its lower fifth or sixth part bear- 

 ing considerable enclosed drift. In like manner the outer por- 

 tions of the ice-sheet, where its thickness was less, had probably at 

 its time of culmination no englacial drift above its lower sixth or 

 fourth or third part. Whatever boulders and other drift became 

 incorporated in the higher portion of the zone reached by the 

 currents flowing upward would be thence carried forward in some 

 regions, as from the Huronian and Laurentian areas north of Lake 

 Huron to the boulder belts in Illinois, Indiana and Ohio, de- 

 scribed by Chamberlin 2 without intermixture with other englac- 

 ial drift brought into the ice by less powerful currents on all the 

 intervening extent, which in the case mentioned is about five 

 hundred miles." 3 



T. C. C. 



1 Geol. and Nat. Hist. Survey of Canada, Annual Report, new series, vol. iv., for 

 1888-89, pages 36-42E. 



2 "Boulder Belts distinguished from Boulder Trains — their Origin and Signifi- 

 cance, " Bulletin, G. S. A., vol. i, pp. 27-31. " The Nature of the Englacial Drift of the 

 Mississippi Basin," Journal of Geology, vol. i, pp. 47-60. 



3 The American Geologist, vol. xii, No. 1, July, 1893, pp. 38-39. 



