54 The American Geologist. January. 1903. 
A Contribution to the Petrography of tiic John Day Basin. By Frank 
C. Calkins. (Bull. Dept. Geol. of the University of California, 
Aug., 1902, vol. 3, No. 5.) 
The John Day Basin has yielded such important contributions to 
vertebrate paleontology that its history is of unusual' interest. This 
paper shows the region in a new light, namely that of an important 
petrographic province. 
Since the begin,ning of Cretaceous time the region has been de- 
fined as a basin of accumulation, ca.iditions of sedimentation alternat- 
ing with volcanic eruptions. It has suffered frequent crustal disturb- 
ance, and has been subjected to more or less erosion both in. recent 
time and in various intervals between volcanic outbursts. The mate- 
rial appears to be largely of pyroclastic origin. 
Considered as a petrographic province, the John Day basin seems 
to be characterized by the fact that its rocks are derived from gab- 
bro-peridotyte and granito-dioryte magmas, with an entire absence of 
rocks of the nepheline group. The analyses show a preponderance of 
soda molecules over potash and a recurrence of anorthoclase-bearing 
rhyolytes in Eocene, Miocene and Pliocene times. 
The order of succession, of types affords a fairly strong confirm- 
ation of Iddings's theory that the normal succession is from intermedi- 
ate to more basic and more acid types. In the Eocene there was a 
complete cycle of this kind : in the Miocene and Pliocene a second : 
a recent ash represents the beginning of a third cycle. 
The great preponderance of pyroclastic material indicates that these 
beds were mainly of terrestrial origin, and affords further evidence 
in favor of the theory of Matthew and disproof of the lacustrine or- 
igin of these beds. i. h. 0. 
Maryland Geological Survey, Volume IV. W- Bullock Clark. 
Since the organization, of the Maryland Geological Survey in the 
spring of 1896 four volumes of the general reports have heein issued 
and three volumes of special reports. 
The present volume, the fourth in the series of general reports, 
possesses the same high degree of practical and scientific excellence 
which has characterized the other publications of the Survey. 
A discussion of Paleozoic Appalachia or the History of Maryland 
during Paleozoic Time by Bailey Willis constitutes Part I. of the vol- 
ume, and comprises the geologic history of eastern North America 
from the pre-Cambrian time to the present. 
The paper opens with a discussion of the geologic processes which 
make geologic history and proceeds with an account of the development 
and wasting of Appalachia. the advance and retreat of the Mediterran- 
ean sea of North America, the growth of Paleozoic coastal plains, 
the accumulation, dislocation and folding of Paleozoic sediments, and 
the formation of post-Paleozoic peneplains. 
Tliis exposition possesses the rare value, which the author's perfect 
familiarity with the great multiplicity of facts presented by the Appal- 
