western, with the result that more frequently remnants of the oldest plains are found in the former than in the latter district. On the other hand, the later plains, but poorly developed along the eastern margin of the Piedmont, become gradually more pronounced westward, the youngest plains being well defined in the drainage basins of the Monocacy and along the Potomac. These old plains, now represented only by remnants of their earlier surfaces, are technically known as peneplains by physiographers. A peneplain is the name given to an area that has been reduced by erosion to approximately a level surface but little above the sea level of the period of its formation, but which may still have unreduced knobs or monadnocks in the interstream areas. Even where these monadnocks have largely wasted away the valley surfaces would naturally be somewhat lower than the divides and would rise slowly to the sides of the valleys as well as from the lower courses of all the streams to their heads. It is important to keep these facts in mind when endeavoring to reconstruct the ancient peneplain surface from the remnants of the old plains that are still left in the Piedmont district. It so happens that after the formation of the oldest peneplain now represented, later erosion has only resulted in the partial development of new plains, highlands, sometimes of wide extent, still remaining as monadnocks in the interstream areas.

The several plains recognized in the Piedmont district are known as the Schooley, the Weverton, the Harrisburg, and the Somerville peneplains, all of which, like the district to which they belong, have been traced far beyond the confines of the state.

STREAM VALLEYS

The present streams are now found in valleys of variable depth that trench the peneplain surfaces. In the eastern division of the Piedmont, where the Harrisburg and Somerville plains are at best but poorly developed, the streams appear for the most part as trenches in the Weverton plain. In the western division, on the other hand, they are found trenching the later peneplains and in the lower Monocacy and Potomac valleys the relations of the streams to the Somerville peneplain are clearly defined.

Some of these streams are more or less adjusted to the underlying rocks, as in the case of Jones Falls to the north of Baltimore; but a large portion of them are discordant, that is, seemingly unaffected by the rocks over which they flow. In the eastern division of the Piedmont the streams flow down the eastern slope of Parrs Ridge in approximately parallel courses to Chesapeake Bay, and in many instances the streams cut across the rocks with little regard to their physical characters. In the case of the Monocacy and its tributaries, we find that there has been little adjustment of the channels, the streams taking their courses across limestones, phyllites, and shales indifferently.

In general, both the main streams and their tributaries show drainage patterns similar to those of the Coastal Plain, and it is not impossible that the stream courses may have been in many instances superimposed on the rocks at no distant time in the past through a mantle of Coastal Plain sediments. Remnants of such a cover have been found far removed from the main body of the Coastal Plain, even as far westward as the Great Valley.

ECONOMIC PHYSIOGRAPHY OF THE PIEDMONT PLATEAU

The physiography of the Piedmont Plateau has materially influenced the settlement and occupation of those who chose this region for their homes.

SOILS. The early settlers, having to raise all their food, naturally sought out the best locations for their broad farms and beautiful estates. On their arrival they found two general classes of farm lands.

The first class embraced the somewhat rolling but extensive tracts of the interstream upland areas. The soils were found to be good producers of corn, wheat, and grass, and the surface not so rough as to make its cultivation forbiddingly difficult. The long, continuous tracts of these interstream areas also made travelling easy, as long as one stayed on the upland, while the stream valleys were shut in and narrow. For these reasons, probably, the various stately manor lands were laid out where the upland expanses were greatest; and the mansions, surrounded by fine.

groves and broad fields, were located on the most promising of the small plateaus. In the earlier days the crops from these broad, upland farms were among the richest in the state and rivalled those of the Eastern Shore.

The second class of farm lands comprised the alluvial loams and sandy flood-plains along the streams. These lands are generally restricted in area, since the valley bottoms are usually narrow and limited in extent. Where streams have opened out lowlands on the marble and limestone areas, rich lands of considerable extent offer most favorable farm sites. The lands along the streams have the advantage of running water and good springs from the hill sides. They are not as well drained, however, as are the lands of the upland, and they are subjected to damaging floods. Comparatively few settlers chose the valley lands at first.

A marked exception to the above rule is found in the Monocacy Valley, where the farm lands are all located on the several benches and terraces leading down to the river or on the bottom-lands belonging to it. So little of the old upland is left that the conditions of occupation are quite different from those farther east.

STREAMS.-While the farming class were searching for good soils and favorable homestead sites, the manufacturers and millwrights were seeking favorable locations for mills, dams, and flumes. The streams of the Piedmont Plateau yielded a great abundance of waterpower, and soon mills dotted the valleys. Each section early came to be supplied with its grist mill, and in due time cotton mills were also built. These industries. in time became of great importance. The flour mills are now generally abandoned, however, only a few of the most favorably situated ones having been able to maintain themselves against western competition. The cotton mills have held out much better, because it has not been until recent years that southern cotton has been spun and woven at home.

The waterpower which the Piedmont streams furnish is not the only wealth which they bring to the state. The land movements during late geological time have caused the streams to trench their courses considerably, and in so doing have rendered accessible the building stones

which were previously hidden beneath the surface. The granites now extensively quarried at Port Deposit would not be so easily obtained and shipped had not the Susquehanna River cut its deep gorge. The locations of the serpentine quarries of Harford County are determined to a greater or lesser extent by the streams which intersect the rock. A formerly important soapstone quarry on Winter Run in the southeast corner of Carroll County was made possible only through the fact that the stream had there cut a deep gorge in a long band of steatitic serpentine. Along the Patapsco and Jones Falls many quarries of granite and gneiss have been located because the stream gorges offered favorable openings or transportation facilities.

It is interesting, by way of contrast, to compare the different conditions under which the Cardiff-Delta slates are quarried. As no stream cuts across Slate Ridge in the vicinity of those two settlements, the quarries have been located along the summit and are worked entirely from above. This is the most difficult way to attack the slates, and as there is no natural drainage for the quarries the water, which is constantly accumulating in the pits, gradually increases the cost of working.

LINES OF COMMUNICATION.-The valleys and ridges of the Piedmont Plateau furnish excellent examples of the way in which topographic features influence commerce and human activities.

One of the first acts of the early settlers of the Piedmont region was to lay out highways. These early roads were not always located advantageously with reference to the topography, but both the divides and the valleys were extensively employed. When the better turnpikes came to be built, however, they were almost without exception built along the divides. The reason for this was that fills and bridges were thereby avoided, and better drained roadbeds, not subject to floods, were obtained. Radiating in all directions from Baltimore, these old turnpikes may be followed into almost every corner of the state, and their location on the more elevated ridges enables the traveller to obtain beautiful views of the richly wooded, rolling uplands and tree-filled valleys.