Editotial Comment. 313 
ered with ver)- perfectly developed small (2mm. long) nephe- 
line and abundant acicular crystals determined by Mr. Wirt 
Tassin as kaliophilite. 
Whether this is the source of the ballast previousl\- de- 
scribed is as yet uncertain. Professor Hitchcock seems to 
think not.* Be that as it may, the definite occurrence of 
this rock on the island is interesting and worthy of a prelim- 
inary note pending more detailed study. g. p. m. 
Recognition of River and Flood Deposits. 
Beliefs honored by long duration of wide and general 
acceptance are yet subject to reconsideration and change, 
not less among geologists than in any other field of investi- 
gation, discovery, and progress. An example of such re- 
vision of an old belief is the recent paper by Prof. W. M. 
Davis, on "The Freshwater Tertiary Formations of the Rocky 
Mountain Region" (Proc. Am. Academy of Arts and 
Sciences, vol. xxxv, pp. 345-373, March, 1900). The exten- 
sive freshwater deposits here discussed, beginning with the 
Arapahoe and Denver formations, allied by their fauna with 
the Crataceous, and continuing, in ascending order, through 
the Puerco, Wahsatch, Green River, Wind River, Bridger, 
Uinta, White River, Loup Fork, and other formations, have 
been ascribed by Eldridge, Cross, Hayden, Newberry, Powell 
Newton, Cope, King, Marsh, Dutton, and others, to sedi- 
mentation in vast lakes. It is shown, however, by this paper, 
that the physical characteristics of these formations, as well 
as their fossils, indicate instead that rivers, meandering in 
variable courses, and in their seasons of flood spreading far 
and wide, were the agents of deposition, bringing the sedi- 
ments from the ever progressing erosion of the mountains. 
The alternations of gravels, sands, and cla^'s, with fre- 
quent cross-bedding and local unconformities, in the deposits 
that have been supposed to belong to the central parts of 
large lakes, are evidently more accordant with the explana- 
tion of these areas as flood-plains of rivers. Shallow pla)a 
lakes of moderate extent undoubtedly existed temporarily 
in many inclosed basins, and on some areas occasionally 
*0p. cit., p. 53. 
