BOSTON MOUNTAIN PHYSIOGRAPHY. 
Upon a careful perusal of Professor A’ H. Purdue’s recent 
article on the ‘‘ Physiography of the Boston Mountains, Arkan- 
sas,’ * it will appear that he dissents from the opinion that there 
is represented in the summit of that range a plain of denudation 
older than that which is usually supposed to be widely developed 
over the Ozark plateau north from the Boston Mountain; and 
this interpretation he bases upon comparison of the erosion 
forms characterizing the two areas, finding that the lower and 
heretofore supposedly ‘newer’? region (considered from the 
standpoint of the physiographer), in reality has by far the older 
type of topography. It seems to the present writer that Pro- 
fessor Purdue has overvalued some of the evidence and mini- 
mized or totally ignored other factors which may have an 
important bearing on the question at issue. 
Ever since my paper on the ‘‘Peneplains of the Ozark High- 
land’’? left my hands I have been conscious of a slight discrep- 
ancy in my interpretation of the topographic development of 
west-central Arkansas, and I wish to take advantage of this 
opportunity to set it aright. 
In identifying the truncated summit of the Boston Mountain 
as a remnant of the same supposed dissected ‘‘Cretaceous”’ pene- 
plain, as is indicated in the summits of the Ouachita ranges 
south of the Arkansas river, I dwelt too strongly on the general 
correspondence in height of the two systems of ridges, and later 
vitiated the conclusion based thereon by developing the prob- 
ability that the present elevated condition of the Boston Moun- 
tain region is largely due to differential uplift in the early part 
of the Quaternary era. 
Dr. C. R. Keyes, in his article on the ‘‘Composite Genesis of 
the Arkansas Valley Through the Ozark Highlands,”3 seems to 
tJour. GEOL., Vol. IX, No. 8, p. 694. 
2 American Geologist, January, 1901, p. 21. 3JOUR. GEOL., Vol. IX, No. 6, p. 486. 
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