~ Reviews—Eocene Glacial Deposits in S.W. Colorado. 329 
VI.—Eocene Gracrat Deposits 1x Sourn-WeEsTERN Cotorapo. By 
W. W. Arwoop. U.S. Geol. Surv. Prof. Paper No. 95 B, 1915, 
pp. 11-26, with 4 plates. 
VERY addition to the growing list of pre-Pleistocene glaciations 
is of interest, and Mr. W. W. Atwood gives conclusive evidence 
for the occurrence of an Eocene Boulder-clay on the plateau of South- 
Western Colorado. In his study of this deposit he has been aided by 
a party of advanced students from Chicago University. This Eocene 
Boulder-clay is situated a mile west of Ridgeway, N.N.W. of the 
mining field of Ouray, at about 7,800 feet above sea-level. It occurs 
near Pleistocene glacial deposits. The Eocene Boulder-clay rests 
upon a wide sheet of Mancos Shale; it consists of a layer, about 
100 feet. thick, of yellowish till containing a great variety of 
boulders, including igneous and sedimertary rocks which range from 
the pre-Cambrian to the Upper Cretaceous. The boulders range up 
to 5 feet in diameter; they are faceted, and a large proportion are 
striated. The Boulder-clay is covered by a slate-covered clay con- 
taining a few very small pebbles, and this bed is also regarded as 
a till. Above it rest the Telluride conglomerates and the San Juan 
tuffs, which are well known from their connexion with the ore 
deposits of Colorado. ‘lhe evidence seems conclusive both as to the 
glacial origin and Eocene age of this deposit, but as Pleistocene 
glacial beds also occur in the same neighbourhood, and as the Kocene 
in this district was a period of mountain uplift, this Boulder-clay is 
an indication of a mountain glaciation and not of any widespread 
glacial climate. 
VII.—Grotoeica, SurvEY oF PorruGAt. 
VHE yearly volume of the Geological Survey of Portugal contains 
; several interesting papers (Commun. d. Comissao do Serv. Geol. 
de Portugal, tom. x, 1914). P. Prevost, in writing on the Devonian 
and Carboniferous of Portugal, demonstrates the presence of all 
stages of these formations save the Middle Devonian. This paper 
contains the description of a new species of Goniatite (Prolecanites 
algarbiensis) from the Culm of Aljezur. V.Sousa-Brandao describes 
at length a universal mineralogical microscope on a new model. The 
same author also describes ‘‘ porphyroblastic phyllites”? from the 
Pre-Cambrian of Aveiro. These are divided into staurolite-garnet- 
phyllites, staurolite-phyllites, and chloritoid-phyllites, which are 
treated in detail. A supplementary paper describes the optic 
orientation of the chloritoid in the above-mentioned rock. Economic 
geology is represented by two papers by P. Choffat, who summarizes 
the evidence for the occurrence of petroleum in the Mesozoic region 
of Estremadura, and describes the history and geology of the garnet 
mines of Suivo which were worked by the Romans. The gems occur 
in a basaltic breccia. The final paper is a valuable bibliography of 
the geology of Portugal and its colonies in 1913, by P. Choffat and 
K. Fleury, which is the eleventh contribution of a similar nature. 
G. We 
