Review of Recent Geological LiteratJire. 185 
face of the upland rise a few monadnocks. In Maryland these residual 
masses are small and few. 
Corresponding to the eastern and western physiographic divisions 
of the Piedmont, there may be made a similar classification on a 
lithological basis. The eastern division is composed of igneous and 
altered igneous rocks; the western of clastic and altered clastic with 
some intrusive rocks. On account of their different degrees of re- 
sistance, these different rocks control in part, the topographic fea- 
tures of the region. Some of the streams are adapted to the structure 
of the rocks; others show no relation to the present structure. The 
latter are superimposed, the eastern ones over Cretaceous and Ter- 
tiary sediments of which the coastal plain is a remnant; the western 
ones over Nev/ark. 
After a summary of the topographic development of the province, 
this section of the work closes with a statement of the relation of the 
occupations of the inhabitants to the character of the soils and streams, 
and to the possibilities of communication afforded by the topography. 
In the Appalachian Region the author finds the topography related 
to geological structure. The mountains and valleys which cross the 
state with a northeast-southwest direction, indicate the trend of the 
hard and soft layers. The region consists of much folded strata and 
the author believes the course of its drainage to have been established 
at the time when the whole district was being reduced to the surface of 
the Schooley peneplain. During that period of erosion the present 
hard ridges caused the development of the streams along the softer 
strata of the synclines; in some cases the arches were so high as to be 
bevelled, their soft cores being thus exposed and giving an oppor- 
tunity for certain rivers to extend their courses' along the anticlines. 
The author finds points of similarity between the coastal plain prov- 
ince and the Appalachian region before ius dislocation. The strata of 
both were deposited in shallow seas which were gradually deepening; 
the materials of both were derived from the Piedmont district. They 
•differ in that the Appalachian strata are Paleozoic, while the coastal 
plain sediments are Mesozoic-Cenozoic. 
Topographically this province is divided into the Blue ridge, the 
Great valley, the Allegheny ridge, and the Allegheny plateau. 
The Blue ridge province consists of the Blue ridge mountains, the 
Catoctin mountains, and the valley between. The Blue ridge pre- 
sents an almost unbroken crest from Gettysburg gap to the gorge of 
the Potomac at Harper's Ferry. It has a precipitous western slope 
and a more gentle eastern one, caused by the easterly dip of the 
Shenandoah limestone and its overlying quartzyte. The Catoctin 
mountain presents a similar structure to the Blue ridge, its promin- 
ence being due to the resistance of the Cambrian quartzyte. Its long 
easterly slope descends to the lowland of the Monocacy valley. 
The valley between these ridges presents its most characteristic 
form in its southern portion where it is drained by Catoctin creek. 
This stream has reduced its basin to an almost base-levelled condition 
