MARYLAND GEOLOGICAL SURVEY 51

tionary War there were seventeen or eighteen forges in operation in
Maryland in addition to the furnaces and other iron works. These
furnaces and forges were built mostly on the tributaries of Chesapeake
Bay. They were all of the same type, using charcoal for fuel with
cold blast and applying the power of the blow cylinder by water
wheels. Some of these furnaces, especially the Catoctin furnace,
furnished guns and projectiles for the Continental army.

During these years attempts were also made to discover and develop
other mineral products. In a letter from Philemon Lloyd to Lord
Baltimore and co-partners in 1722 the writer speaks of the discovery
of copper ore and other minerals. A report made by the Governor
and Council to the Board of Trade of London in 1748 states among
other things that " there are in the Province great shews of copper
in many places, but of the several attempts that have been made to
discover veins of "that metal none has yet been made that quitted cost. "
It was probably shortly after this that a party of English miners
opened the Liberty and Mineral Hill mines. They built a small
smelting furnace on the Deer Park tract of land near the latter mine
where they smelted the ores, and must have produced considerable
quantity of copper, as shown by the large amount of rich slags and
residue left at the furnace, which nearly a century later were hauled
to Baltimore and profitably reworked. Operations at these mines
ceased for a time with the opening of the Revolution.

In various letters to Lord Baltimore during the period above de-
scribed, references are made to the natural resources of the state and
accounts are given of the different types of rock, of the condition of
the soils, and of the general character of the country, based particu-
larly on more extended explorations of the central and western
portions of the colony. Before the opening of the Revolution there
was already a wide acquaintance with the broader features of the
physiography and mineral products of Maryland.

The determination of the boundary line between Maryland and
Pennsylvania was the object of one of the most famous surveys made
in this country and one which added much to the existing knowledge
regarding the physical features of the state. After numerous con-
troversies a deed was finally executed between the heirs of Wm. Penn