have been injected molten rocks which to-day appear as pegmatite and diabase dikes. The texture of the rocks, as a result of recrystallization under great pressure, presents a characteristic foliation often much contorted. This may be widely seen in the more schistose rocks. Even the eruptives have frequently developed a similar schistosity. The rocks have been extensively folded and faulted, great overthrusts occurring which have greatly complicated the structure of the district. The higher upland surface of the Piedmont represents the old Schooley peneplain, while at lower levels have been developed the Weverton and Harrisburg peneplains, the last forming the floor of the Frederick Valley and some of the smaller streams which trench the Piedmont area.

TOWSON is situated for the most part on the crystalline Baltimore gneiss, the higher portions of the town reaching the ridge of Setter's quartzite, while to the north of this in the various valleys stretching to the north, west, and east may be found the so-called Cockeysville marble which has been so extensively worked for economic purposes. Towson lies on the surface of the ancient Schooley peneplain, this upland being more or less dissected by the streams which have cut their way through the overlying rock.

BELAIR is located on the broad upland plain of the Piedmont, known as Schooley peneplain, a large area of gabbro forming the underlying rock to the north and west, while the gneiss is the basal rock to the east. Some miles to the northward the Maryland and Pennsylvania Railroad runs through a small gorge capped by quartzite (Rocks of Deer Creek), while near the state line at Cardiff is the famous Peach Bottom slate district (Slate Ridge).

WESTMINSTER is near the center of the Piedmont area, and is situated on the broad plateau known as the Weverton peneplain, which in this district has not been deeply trenched by the stream channels. The most common rock of the region is the phyllite, intercalated with which are numerous lenses of crystalline limestone and basic volcanics, especially along the line of the railroad to the west of the city (Union Bridge). At several points in the center of the county are dikes of diabase rock.

ELLICOTT CITY nestles in the gorge of the Patapsco River in the midst of an area of gabbro cut at many points by dikes and larger bodies of granite, while farther west are numerous pegmatite dikes which have been the source of commercial feldspar.

ROCKVILLE is located in the schist district of the dissected central Piedmont. To the south is an area of basic volcanics, to the east are granites and diorites, and to the west dikes of serpentine and disbase. About Seneca and farther west is a large district composed of Newark breccia, sandstones, and shales (Triassic).

WESTERN MARYLAND

This region has been hitherto described under the name of the Appalachian Region and presents a great diversity in its physiography and geology. The rocks have been deformed into a series of folds, much faulted to the east, but generally becoming flatter to the west. The crests of the mountain tops represent the ancient Schooley peneplain, while the lower ridges and valleys successively represent the Weverton and Harrisburg peneplains, while along the Potomac and its larger estuaries terraces of later date may be observed. The rocks comprise the various Paleozoic formations from the Cambrian to the Permian, with here and there ancient igneous rocks, while along the eastern margin of the district are to be found the Triassic sandstones and shales. The Potomac has cut its way downward from the ancient peneplain over which it flowed across the numerous sandstone ridges of the district, while its tributary streams have for the most part made their channels in the softer rock.

HAGERSTOWN is situated on the broad valley floor of the Harrisburg peneplain, the underlying rocks being limestone of late Cambrian and early Ordovician age. A few miles to the west of the city extending from Williamsport to the northern border of the state is a low ridge of late Ordovician shale (Martinsburg). Along the mountain sides the Weverton peneplain is indistinctly shown, but in the level-topped crests of South (quartzite) and North (sandstone) mountains are remnants of the old Schooley peneplain. Fossil remains of the early Paleozoic formations

showing the marine character of most of these formations may be collected at times in the quarries and railroad cuts.

CUMBERLAND is located in the Potomac Valley and its tributary Braddock Run and is largely underlain by Silurian (Clinton) shale, often rich in fossils, showing the marine origin of the deposits. Cumberland is bounded on the west by Wills Mountain (Juniata and Tuscarora sandstones), which in its level-topped crest line shows with exceptional clearness the ancient level of the Schooley peneplain that once extended over the entire region before the valleys were cut in the softer beds. To the west as well as to the east of Wills Mountain, which represents the axis. of a great fold, come in succession the various Silurian, Devonian, and Carboniferous formations. On the western limb of this fold in beds of Silurian age occurs the Devils Backbone. These various formations are often rich either in marine fossils or terrestrial plant remains, and Cumberland has long been classic ground for the geologist. The deep valley gradually cut by Braddock Run through the Wills Mountain anticline is of unusual geologic interest, while the numerous terraces in and adjacent to the city are among the best in the valley of the Potomac. OAKLAND is located in the valley of the Youghiogheny River, the waters of which reach the Ohio River. It is situated on the Devonian shales (Jennings), which stretch as a broad belt from northeast to southwest across the county. East and west of Oakland the sandstone ridges constitute remnants of the ancient Schooley peneplain which in Garrett County must have stood at quite 3500 feet in elevation. Both in the Potomac basin to the southeast and the Oakland basin to the west, the Carboniferous deposits afford many localities from which both animal and plant remains. may be secured. Oakland itself stands near the center of a great fold which is more flattened here than in the more eastern parts of the Appalachian district.

SOUTHERN MARYLAND

This area is embraced within the limits of the Coastal Plain and is composed of various geological formations from the Lower Cretaceous to the Pleistocene. The deposits are made up chiefly of gravels, sands,

clays, and marls, which are in the main unconsolidated and dip at a very low angle to the southeast. The district has been subjected to a series of elevations and depressions since late Tertiary time, with the result that a complicated series of terraces has been developed along the margin of the Coastal Plain and in its various river channels. These later Tertiary and Pleistocene terraces succeed one another from above downward, the sea at the present day being engaged in the formation of the last of the series beneath the shallow marginal waters. The streams are largely tidal, the channels being submerged at the time the waters of the Atlantic filled the basin of the Chesapeake during the last great depression of the late Pleistocene epoch.

ANNAPOLIS is located on the Talbot terrace (late Pleistocene), the escarpment of the Wicomico terrace (middle Pleistocene) being found. near the western margin of the city. On the Severn River nearby the Eocene strata occur beneath the Talbot, containing at many points characteristic marine fossils (mollusks, sharks' teeth, etc.), while farther up the stream occur beds of Upper Cretaceous age, also fossiliferous, dipping beneath the Eocene. The uppermost of these (Monmouth and Matawan) contain marine fossils, while the subjacent formations (above Round Bay), consisting of white sands and clays (Magothy and Raritan), contain at times terrestrial plant remains. To the south of Annapolis about South and West rivers occur the Miocene formations overlying the Eocene, the diatomaceous deposits of the latter being especially well represented around Herring Bay.

UPPER MARLBORO is situated on a tributary of the Patuxent River on the dissected upland surface of the Coastal Plain, the Eocene formations extensively outcropping in the surrounding region. Numerous marine. fossils of Eocene age have been found in the greensand beds. In the valleys of Western Branch and the nearby Patuxent, the Talbot terrace is in places well developed, while at higher points remnants of both the Wicomico and Sunderland terrace are also found. Some miles to the south of Upper Marlboro the Brandywine terrace is typically developed, the broad plain in this region being the most extensive on the western side of the Chesapeake.

LA PLATA is situated near the southern end of the Brandywine terrace, although the plain is here much dissected, the lower terraces occurring not far away in the various stream channels. The underlying deposits are of Eocene age, generally greensand marls, frequently rich in fossil remains. PRINCE FREDERICK is situated on the Sunderland terrace, which forms the crest of the highland between Chesapeake Bay and Patuxent River. To the east and west of the town the stream channels cut through to the underlying Miocene deposits which in Calvert County have furnished a great wealth of fossil remains, all of the Miocene formations being here well developed. The Wicomico and Talbot terraces appear one below the other at various points along the margin of the Chesapeake and Patuxent.

LEONARDTOWN is likewise situated on the Sunderland terrace with successively lower terraces appearing both along the Potomac and Patuxent river fronts and frequently extending up the tributary channels. Beneath these terraces, over a large part of St. Mary's County, are found the several Miocene formations, rich in marine fossils, and extensive collections both from this and adjacent counties now enrich the museums both of this and foreign countries.

NORTHERN EASTERN SHORE

The northern Eastern Shore is chiefly confined to the Coastal Plain. the deposits in general being similar to those found in Southern Maryland. They consist of representatives of the various formations from the Lower Cretaceous to the Pleistocene. The several terraces described for Southern Maryland are here developed, although the Brandywine and Sunderland terraces are much less extensively represented in this area. On the other hand, the Wicomico and Talbot terraces are much more largely developed and present broad terraced plains that are highly characteristic of the northern district, the escarpment separating the Talbot from the Wicomico terrace being one of the most distinctive physiographic features in the region. Tidal rivers extend far into the region, even the upper courses of the streams being for the most part sluggish because of the relatively slight elevation of the land.