Febei'abv 15, 1893.] 



SCIENCE. 



175 



that liardly deserves a place in modern 

 teaching. Political geography is undiffer- 

 entiated history. Commercial geography is 

 the elementary phase of economics. The 

 distribution of plants and animals leads tlie 

 way to botany and zo()logy ; the chief value 

 of this subject coming from the emphasis 

 that it gives to those physical features and 

 conditions of the earth that determine the 

 distribution of life ; when it is made a 

 basis for the introduction of classification 

 and terminology, it is misused, for these 

 matters need deliberate study with a method 

 and discipline of their own. The subjects 

 of oceanography and meteorologj^ involve 

 considerations and disciplines so different 

 in many respects from those which char- 

 acterize the study of the lands that they 

 fully deserve separate names and treatment ; 

 but their teachings must be frequently drawn 

 on for use in physiography. 



Contributions from many subjects, as- 

 tronomy, physiology, botany, zoology, his- 

 tory and economics, are merged into a single 

 elementary study — geogi-aphj- — in the ear- 

 lier school years ; all are expanded and sep- 

 arately treated in later school years ; all de- 

 serve to be treated over again afterwards in 

 the broader way characteristic of college 

 teaching ; and all include broad fields for in- 

 vestigation in the university. 



Physiography being particularly directed 

 to the study of the lands, must of necessity 

 in its higher researches give due considera- 

 tion to themore minutefeaturesof land forms 

 and their development — ^subjects which re- 

 cent writere name gi'omorphologj' and geo- 

 morphogenj' — for tiic sufficient reason that 

 a close understanding of the development 

 of land forms greatly aids the observation, 

 description and recognition of the forms 

 themselves ; and that the knowledge thus 

 only to be gained of the forms of the land 

 is essential as a preparation for the careful 

 study of their relations to man and other 

 inhabitants of the earth. 



As thus explained, physiography is an 

 outgrowth of geologj' ; and geology, especi- 

 ally field geologj-, is a necessary prelimi- 

 nary discipline both for those who would 

 undertake the higher study of physiography 

 and for those who would reduce it to the 

 simplest form of expression for early school 

 use. 



MEiVXIKG OF THE TERM, BASELEVEL. 



Since the introduction of the term base- 

 level by Powell twenty years ago, its use 

 has become popular but unhappily its mean- 

 ings have not been well defined. A sub- 

 division of the work that the word has been 

 made to do now seems desirable. It should 

 be restricted rather closely to its original 

 meanings, and newer terms should be em- 

 ployed for its secondary meanings. Powell 

 originally wrote : " AVe may consider the 

 level of the sea to be a grand base level, 

 below which the ch-y lands cannot be eroded, 

 but we may also have, for local and tempo- 

 rary purposes other base levels of erosion, 

 which are the beds of the principal streams 

 which carry away the products of erosion." 

 (Colorado Eiver of the West, 1875, 203.) 

 By using a few qualifying adjectives, there 

 need be no confusion between general, 

 local and temporary baselevels. "Wiien 

 unqualified, the general baselevel, or sea 

 level, should be underetood. 



When a region has been ba.selevelled 

 (the verb being here made from the noun, 

 after the ordinary English fashion), the 

 surface thus produced is often spoken of as 

 a ' baselevel.' For example, J. S. Diller 

 writes: ''It is evident that a general base- 

 level of erosion must have originated ap- 

 proximately at sea level. This is the only 

 position in which a very extensive baselevel 

 can originate. If we now find such a base- 

 level at a considerable elevation above the 

 sea, its position furnishes evidence that 

 since the baselevel was formed the country 

 has been uplifted." (Chicago Journal of 



