W. J. McGee—Artificial Mounds of Northeastern Iowa. 275 
The last three classes of mounds are commonly found on 
ridges separating water-courses, though they sometimes occur 
on “benches” and “bottoms.” Few of the prominent ridges 
on either shore of the Mississippi from Dubuque to the Minne- 
sota line are free from them. Excavations from which the 
ounds sometimes appear on rocky spurs, whither it would 
seem their constituent materials must have been transported 
from considerable distances. 
aving had occasion to survey many groups and systems of 
mounds, recording all measurements for the purpose of plotting 
the works, the writer has been struck by the constancy of certain 
dimensions and the harmony observable in all, whatever the 
measurement in their erection—a peculiarity which seems to 
have been hitherto overlooked, so as the mo ds of the 
Northwest are concerned. use of such a unit being cer- 
and Turkey Rivers) The width of the ridge now 
a mile, and it is usually quite narrow. It rises from two hun- 
dred to three hundred feet above the level of the rivers, and 
terminates just above their junction in a perpendicular ledge 
of Galena limestone one hundred and fifty feet high, twenty to 
i | nd feet long. » The system of 
8 extends for six miles in a northwesterly direction from 
i mow em ments, ani- 
Beginning at the end of the 
