174 The American Geologist. ^arch, 1904. 
portant a group of land forms as mountains has never yet been 
thoroughly treated in a physiographic sense, while the organic 
responses to inorganic controls are as a rule not classified by 
geographers at all ; yet a comprehensive scheme of classifica- 
tion should certainly provide systematic places for the organic 
responses as carefully as for inorganic controls. In the absence 
of a generally accepted scheme of classification, it is natural 
that items of one kind and another should be neglected in text- 
books and elsewhere; for it is well known that incompleteness 
of treatment goes with unsystematic methods. So simple and 
manifest a response to the globular form of the earth as is af- 
forded by the wide extent of modern commerce is seldom men- 
tioned in conection with its control. The many important and 
interesting responses to the eternal and omnipresent force of 
gravity are not habitually treated as geographical topics at all ; 
nor is the definition of boundaries in terms of meridians and 
parallels usually recognized as a response that civihzed na- 
tions now habitually make to the form and rotation of the earth, 
\v\\i-n they have occasion to divide new territory in advance of 
surveys and settlement. Yet surely all these responses to en- 
vironment deserve systematic mention when the earth is de- 
scribed as a rotating gravitating globe, just as the location of 
villages and the growth of cities at some point of advantage to 
their inhabitants deserves mention in the pages given up to 
geography of the more conventional kind. The development of 
a well-tested scheme of systematic geography may therefore 
be urged upon every geographer as a problem well worthy of 
his atention. A practical step toward the construction of such 
a scheme is evidently the accumulation of its items that call for 
classification ; therefore, let the geographer study the world 
about him : and a most eflrectual aid in the accumulation of 
items is found in searching for the organic response to every 
organic control, and for the inorganic control of every inorgan- 
ic response that comes to one's atention ; therefore, let the ge- 
ographer think carefully as he looks about him over the world. 
It can hardly be doubted that the explorer who goes abroad or 
the student who stays at home will make better progress in his 
investigations in proportion to the completeness of the system- 
atic scheme with respect to which he consciously carries on his 
work. I would therefore urge the development of the habits 
