352 
BRIDGING THE AGES OF ICE 
continent. At the time the record was carefully preserved in 
one of our leading scientific magazines. Were it not for this 
circumstance a great scientific discovery might soon have passed 
into oblivion and lost. Long since the mural faces succumbed 
to the effacing effects of rain and frost, until they were worn 
down to gentle hillside slopes, grass-covered and tree-dotted. 
In recent extensive grading operations on the new Capitol 
grounds the celebrated Glacial sections are again laid open to 
sky. The site is now to be preserved for the ages to come. It is 
already to be marked by a permanent monument erected by the 
State of Iowa. A beautiful and substantial bridge spans the 
sunken speedway where the sections were best exposed. 
This monumental site, on the brow of Capitol Hill, is now really 
one of the scientific wonders of the state. Geologically, however, 
its interest is indeed global. Bearings of these local . sections 
upon the broader aspects of the basic problems concerning the 
great Ice Age seem worthy of brief relation. For many years 
after Louis Agassiz first gave to the world his theory of glaciation 
— one of the most brilliant generalizations of modern science — 
earth students in the field were occupied mainly in gathering facts 
and details. With the accumulation of these records came new 
generalizations. Gradually it came to be realized that the original 
notion was not nearly so complete as was in the beginning sup¬ 
posed. ' 
Finally it began to develop that instead of a single Glacial 
epoch there were probably several successive Ice Ages. In the 
great, world-wide controversy which was warmly waged on this 
subject for more than a generation Iowa chanced to bear a 
conspicuous part. Not the least interesting feature was it that in 
this State were found the first undoubtable evidences of the exis¬ 
tence of more than one drift-sheet separated by a thick deposit 
of fine, wind-deposited loam. In after years this observation 
proved to be the most critical criterion in the argument for a 
multiple rather than a unal character of the Ice Age. More¬ 
over, Iowa men made this important discovery. In this State 
were finally differentiated five great Glacial mantles. At the 
present day the Iowa Classification of the great Ice Age de¬ 
posits is recognized the world over. 
