PRELIMINARY NOTE ON THE SO-CALLED “LOESS” OF 
SOUTHWESTERN IOWA. 
James Ellis Gow. 
While exploring Adair county in the interest of the Iowa State 
Geological Survey, the writer made some observations upon the sur- 
face soil of that region, which have led him to differ with the conclu- 
sions of other geologists who have described the same soil in adjoining 
counties. This soil has usually been described as Iowan loess, sometimes 
simply as loess. The long controversy as to the nature and origin of 
the Mississippi valley loess has left in its trail such apparent confusion 
as to the precise meaning of the term that it seems almost necessary 
to define it anew before attempting to make use of it in a scientific way. 
The writer will accordingly begin his argument by defining what he 
understands by the term ‘ ‘ loess. ’ ’ 
WHAT IS LOESS? 
This term was first applied by European geologists to the extensive 
deposits of homogeneous fine-grained clay found in China and the up- 
lands of centra] and northern Asia. This clay , is distinctive in its 
characteristics. It is so fine grained in texture as to be readily held in 
suspension in the air, and when deposited in any mass solidifies so per- 
fectly that vertical banks disintegrate very slowly under the action 
of water, and may stand for many years. A clay of precisely these 
characteristics is found in Iowa, around the border of the Iowan drift 
sheet and in the valley of the Missouri river, and has long been known 
as loess. It was first regarded as loess because of its texture and physical 
characteristics. It was long believed by many geologists that the loess 
was formed directly by aqueous agencies ; but it would have been a mis- 
take to say that it was loess because it was laid down under water, else 
stratified sands, gravel, and alluvium would also have to be classified 
as loess. It is now generally believed — on evidence that seems to the 
writer to be absolutely conclusive — that the loess is of aeolian origin. 
But it is a mistake to say that it is loess be.cmi.se of its aeolian origin, 
else the material of sand dunes would have to be considered as loess. 
