THE GEOLOGICAL SECTION OF MICHIGAN 681 
be necessary. It need not be said that there are many things and 
many divisions in the geological column upon which further light 
could be thrown, and it is hoped that before long the Paleozoic 
geology of the Upper Peninsula may receive more careful attention. 
But it is the state geologist’s feeling that it is well to be sure one is 
right before going ahead in any change of names, since any such 
change renders reports less readable even to the geologist, much more 
so to the teacher, engineer, and others who make casual use of them. 
This is much more the case when a number of new names are brought 
in at once. In regard to the scientific questions involved, see the 
article, “The Geologic Day,” Journal oj Geology, 1906, p. 425. 
One general remark should be made. The point of view of the 
state geologist is largely that of a student of well records and of the 
drillings returned from them, in which the fossils play next to no part. 
Not only is the point of view of Dr. Grabau that of a paleontologist, 
but this must also be remembered, that the study of the paleontolo- 
gist on outcrops is, in a broad and general way, the study of forma- 
tions nearer their margins and more likely to be of some other type 
than simply marine, and if marine deposits, more likely to be deposits 
of the littoral, and of extreme transgression. 
In studying and comparing well records it is a notable fact that 
certain parts of the geological column seem to be persistent and 
easily correlated from well to well. Others vary markedly, even in 
extremely short distances. ‘These are the points where the uncon- 
formities come in. 
The columnar section is divided into two parts, on different scales, 
since the thicknesses of the pre-Ordovician units are much greater 
than those of the later ones. The thicknesses in the column are 
those derived from wells where the formation is as flat as possible 
and as far removed from its source. An attempt has been made to 
draw the column to scale, giving each formation something like its 
minimum thickness when not obviously cut off by erosion, uncon- 
formity, or overlap. The numbers placed along the side, however, 
show also the customary range up to the greatest thickness of which 
we can be reasonably sure. Still greater thicknesses may and often 
have been estimated, but in our judgment may not have had due 
allowance made for faulting, initial dip, or crushing. 
