QUARTZOSE BOtJRDERS FROM CENTERVILLE 
123 
north of the present borders of the state of Iowa. There can 
also be no question but that the conglomerates under consideration 
are of purely aqueous origin and were the result of coarser peb- 
bles being imbedded in a paste of finer sand, close to the ancient 
shore line, which paste was eventually consolidated by the process 
of infiltration of silicious material into a compact quartzite mass. 
True quartzitic character of the matrix in boulders of this charac- 
ter has in the past been quite generally considered as indicative of 
great age, and by many It has been thought that such a character- 
istic precluded the probability of boulders of this type originating 
in the Paleozoic strata as we are familiar with the same within 
the confines of the’great central inland basin. This is particularly 
true of students of geology who have not had the opportunity of 
doing extensive field work covering extended areas. 
A train of boulders of this identical and highly similar types are 
to be found scattered at Intervals over the surface of the Kansan 
and succeeding glacial drifts from north to south across our entire 
state and into southern Minnesota, and when found they have 
usually been roughly assigned to one classification and alluded to 
as of “Huronian age” with an air of finality, little or no consid- 
eration being given to the evidences bearing out this conclusion, 
other than a superficial examination showing quartzitic character 
of the matrix, and the appearance of veneration. Whenever any 
effort is made to assign them definitely, to any specific subdivision 
of Huronian time, which occurs but rarely, they are usually con- 
sidered to belong to the lower member of the Huronian Group, 
known as the Sturgeon Quartzite, which according to Chamberlin 
is frequently conglomeratic in character. 
The writer has himself personally examined specimens through- 
out the drift of northwest Iowa and southwest Minnesota, which 
contains pebbles of all sizes and of a similar material, thence pas- 
sing insensibly through the coarser gravels to the finest quartzitic 
sandstone to quartzites, the graduation into the arenaceous group 
being unbroken, and can therefore upon first hand information 
vouch for the fact that the place of origin of the boulders in 
question must certainly exist above the northern limits of the 
state of Iowa. Like others he has glibly spoken of them as 
Huronian or Algonkian and confidently permitted the matter to 
be disposed of thusly. This lumping of all such material together 
indiscriminately under one classification, as Huronian, I shall pres- 
ently show is erroneous, and would suggest that students of 
