hmus of Darien," was occupied with lakes,
some of which were immense in size. In after times thousands of small
lakes took their place, and these have finally disappeared. Many of
these were expansions of the rivers, like most modern lakes. The old
valleys are now occupied by a diluvial deposit, the counterpart of the
Loess of the Rhine, and almost the same in composition. The
agricultural future of all that valley region is very promising, for
from some mysterious cause, the rainfall seems to be increasing over
the whole area. Buried trees of great size prove that Nebraska has not
always been the grassy waste it now is, and the revolutions of nature
may restore its forests. Mr. Aughey figures some arrow-heads which he
found in this deposit fifteen and twenty feet from the top, and in such
a position as to assure him of their true age. Leaving the admirable
geological study of Dr. Peale, we come to Mr. Eudlich's examination of
the San Juan mines. This is a kind of work which government explorers
should do more of, though until the mines are worked deeper, the
information obtained is not very full. The veins are reported to be
probably of Cretaceous age, or they may date from the beginning of the
Tertiary. Dr. Hayden reports that when the coming season's work is
finished "the most rugged and mountainous portion of our continent"
will have been surveyed. It is his intention to map it in an atlas of
six sheets, each covering about 11,500 square miles. The cartographical
work of the survey is excellent. This volume contains eighty-eight maps
and views, executed in a most creditable manner.

[11] "_United States Geological and Geographical Survey of the
Territories._" F. V. HAYDEN, United States Geologist in charge.
Annual Report, 1877. Colorado and adjacent Territories.
Government Printing Office.

--We have also received two of the "Miscellaneous Publications"[12] of
the survey, one being the last and crowning work of America's great
invertebrate palaeontologist, Dr. F. B. Meek.[13] The names "Meek and
Hayden" have an association in American scientific work that is
historic, and in the "Report on Invertebrate, Cretaceous, and Tertiary
Fossils of the Upper Missouri Country" are assembled the results of
painstaking labors extending through many years. The volume is worthy
to stand as a monument to such an author. The introduction contains a
description, in the author's characteristically concise styl