Glacial Outlook from Iowa

Iowa and the upper Mississippi basin are, as is now quite generally known, in possession of the most complete Glacial succession in the whole world. With its great wealth of recorded observation the trend of inquiry turns not so much to unearthing more tillsheets, as was the prognostication of the enthusiastic Calvin, as it is to ferret out the most plausible causes of periodic glaciations, and especially to test their astronomical relationship