OCTOBER 22, 1897. ] 
best geographers from abroad was of very 
great value, particularly to many of the 
younger men. On every hand good fellow- 
ship prevailed, and every one present felt a 
new impulse to work from the inspiration 
of the meeting. Many of the visitors took 
the trip tothe western coast after the meet- 
ing, on which, according to reports, fully as 
great results geographically were obtained 
as at the meeting. Not only must Canada 
feel a new scientific movement of progress 
from the meeting, but the United States as 
well must join in the good to be obtained. 
The visitors from abroad all agreed that 
they had gained much from the trip more 
helpful than mere information. All the 
Americans trust that they have been able 
to give in return a part of what they have 
received, and that this international meet- 
ing may help the cause of geography on 
on both sides of the water. 
Ricwarp H. Dopce. 
IS THE DENVER FORMATION LACUSTRINE 
OR FLUVIATILE ? 
Tue usual interpretation of stratified de- 
posits refers them to accumulation beneath 
water, either in the sea or in lakes. But 
_ many observers have recognized the ability 
of rivers to form stratified deposits more or 
less extensive; hence the mere occurrence 
of stratification might suggest fluviatile as 
well as lacustrine or marine origin; and 
some other sign than stratification would 
be needed to distinguish among these sev- 
eral conditions of deposition. When fossils 
are contained in the strata it is commonly 
easy to determine at least whether they 
were of salt or fresh water origin; but 
when without fossils, or when containing 
only fresh water or land fossils, it may be 
still a question whether the deposits were 
formed in lakes or rivers. It has been per- 
haps assumed that river deposits must be 
local, while lacustrine deposits may be wide- 
spread ; but the immense fluviatile deposits 
SCIENCE. 
619 
of the Indo-Gangetic plain must suffice to 
free the products of aggrading rivers from 
narrow bounds. Blandford’s account of 
the vast deposits of waste in long sloping 
plains at the base of mountain ranges in 
the interior basins of Persia, as well as the 
description of similar accumulations in 
our western country, shows that extensive 
stratified deposits may be formed in regions 
where even rivers are not a constant or con- 
Spicuous agency ; and the believer in the 
competency of small processes to produce 
great results if time enough is allowed 
would find it difficult to set limits to the 
area or thickness of formation of such origin. 
The distinction between true lacustrine 
sediments and true fluviatile sediments may 
be made in part by their composition and 
structure and in part by their fossils. Riv- 
er deposits are of variable sequence, coarse 
and fine, evenly or unevenly arranged, 
eross-bedded, ripple-marked and _ sun- 
eracked. Mid-lake deposits are of fine 
texture and even structure, becoming coarse 
and irregular only near their margin. A. 
characteristic lacustrine fauna, enclosed in 
mid-lake silts, should be easily distinguished 
from the mixture of land and water fauna 
that might be preserved in coarser lake- 
border deposits or in the coarse and fine 
strata of normal river deposits. In the ab- 
sence of a fauna, it might be difficult to 
distinguish lake-border deposits from river 
deposits ; there might indeed be difficulty in 
separating lacustrine silts from the fine silts 
of river flood-plains, if fossils were wanting. 
Gilbert’s interpretation of some of the 
newer deposits on the Plains of Colorado 
near the Arkansas river as of fluviatile 
origin, and the adoption of his idea by the 
geologists of Kansas for the eastward ex- 
tension of the same formations, has recently 
given practical application to the above 
generalities. Penck gives in his Morphologie 
a number of European examples of depos- 
its ordinarily called lacustrine, but which 
