224 PHYSIOGRAPHY, GEOLOGY AND MINERAL RESOURCES

gany county, has for a long time been highly regarded. There are
numerous cold chalybeate springs scattered throughout western Mary-
land, 'but there has been as yet no attempt to introduce the waters or
develop the properties upon which they are situated.

Very few springs of mineral water of more than local reputation
are reported from the Coastal Plain. The Mardella of Wicomico
county is very well known and the waters have been placed upon the
market. Several other springs, which have only a local value, are
reported from the eastern and southern counties, among them a sulphur
spring situated at St. Michael's, Talbot county.

THE ROAD MATERIALS.

The state of Maryland is well provided with road-building materials,
although their character varies widely, some being far better adapted
for the purpose than others. The question of transportation is, how-
ever, so important that the stone of greatest value cannot always be
employed, yet there is no section of the state where there are not
some materials sufficiently close at hand to render them available.

The best road-building materials in Maryland are the basic igneous
rocks, which are found well developed throughout the area of the
Piedmont Plateau. Of these there are several types, viz., the gabbro,
the peridotite and pyroxenite, and the diabase. The gabbro or " nig-
gerhead " rock, as it is locally called, is most widely distributed and
occupies an extensive area throughout the eastern portion of the
Piedmont belt in Cecil, Harford, Baltimore, Howard and Montgomery
counties, the largest regions being found in central Harford and
southern Baltimore counties. This rock is rather tough and difficult
to work, but affords a valuable and permanent road metal. The
peridotite and pyroxenite are not as extensively developed, but occupy
very much the same area as the gabbro. These magnesian rocks are
somewhat more easily worked than the gabbro, but do not have their
wearing qualities. The most valuable of all these rocks is the dia-
base, which is so extensively used for road-building purposes in New
England and New Jersey and which occurs in several long and narrow
outcrops in Baltimore and Howard counties, but far better developed