20 
GEOLOGY: N. M. FENNEMAN 
is an intimate intermixture of several types which are, however, so 
related genetically that both are accounted for by the same history. 
Indeed, while this work has no direct reference to teaching, there is 
something almost final about the requirement that a province or sec- 
tion should be a suitable unit for scientific treatment. This is quite 
as necessary from the standpoint of government surveys as from that 
of the university. 
The committee distinctly disclaims finahty for this work. With 
further investigation and more exact mapping some of the boundary 
lines here given may be shifted. The lines on this map were located 
by aid of the largest scale topographic and geologic maps available. 
Parts of the country are, however, imperfectly mapped, hence, with 
respect to exact plotting, the values of the several Hues are unequal. 
All are necessarily generalized. As the result of future studies it may 
well be that the rank assigned to some of the units will be changed. 
Units of still lower orders will of course be made. Above all, the pres- 
entation of this map is not intended to preclude the use of other kinds 
of physical divisions like those of Supan, De Mar tonne, Herbertson, or 
Dryer. It is beHeved, however, that for a map of physiographic divi- 
sions, the main features of the one here presented will not be greatly 
changed. 
The uses of such a map are of two general classes, (1) for scientific 
(explanatory) description, and (2) for comparative studies with other 
geographic elements. In the former, physical features are looked upon 
as the product of geologic processes, in the latter they constitute fac- 
tors or conditions of life and human activity. In the former aspect 
they are an effect; in the latter a cause. The potency of such causes 
can only be known when statistics of population, agriculture and in- 
dustry and even politics are graphically shown with due respect to 
natural units. It is plain that if matters statistical are to be repre- 
sented on a map of natural divisions, and things human are to be dis- 
cussed in terms of their physical setting, the value of the relations dis- 
covered will depend largely on the character of the natural divisions 
and their proper delimitation. 
In the following table the names of major divisions are printed in 
italics; the provinces are numbered, and the sections lettered. The 
province number and the section letter correspond to those on the map. 
Table of physiographic divisions of the United States 
Laurentian Upland. — 
1. Superior Upland 
