DAVIS: MOUNTAIN RANGES OF THE GREAT BASIN. 131. 
tory examples of southern Oregon. In view of this relation of the Basin 
ranges to the problems of systematic physiography, the opportunity of 
seeing some of them last summer was especially welcome, even though 
~ the time that could be given to them was brief. The conclusion reached 
was that faulting has recently exercised and indeed still exercises a 
dominant control over the uplift of all the larger mountain ranges ob- 
served, but that erosion has greatly modified the form which would be 
produced by faulting alone, and that the prefaulting form is for this 
reason generally not recognizable. 
Theoretical Considerations. — It seems desirable to present the observa- 
tions that have led to this conclusion in an order that is suggested by a 
deductive consideration of the problem, such as is necessarily entertained 
in the establishment of ideal physiographic types of mountain forms, In 
this way the complete ideal types of carved block mountains may be 
first carefully conceived and visualized in the imagination, all their essen- 
tial features being systematically developed. The observed elements of 
form may then be described in their proper relation to the whole of 
which they are believed to be but parts. Pl 
The various types thus conceived in the imagination must represent 
all the hypotheses by which the facts in hand may be explained, the 
advantages that follow from a due consideration of “ multiple-working 
hypotheses” having been convincingly set forth by Chamberlin. In 
publication, however, it is permissible to give relatively little space to 
those hypotheses which have been proved incompetent during the pro- 
gress of an investigation, and to set forth in detail only the one which 
has gained — in the author’s opinion at least — the rank of a successful 
theory. For this reason, the following pages are chiefly devoted to a 
consideration of the Basin ranges as dissected fault-block mountains. 
The author feels that some apology is needed for his writing on a field 
where his own observations are very limited in comparison to those of 
others who have a much wider experience in the Cordilleran region. His 
reason for adding yet another essay to the already abundant literature 
on the mountain ranges of the Great Basin is chiefly that the articles 
thus far published have not included a detailed analysis of the problem 
in hand, and in particular that the effects of erosion upon the faulted 
mountain blocks have received but little consideration. Gilbert’s brief 
statement, written thirty years ago as the result of his first western ex- 
peditions in 1871, 1872, and 1873 (b, 40, 41), is hardly more than a sum- 
mary of conclusions. Russell explains the Basin ranges as having been 
“formed by the orographic tilting of blocks that are separated by pro- 
