108 HISTORICAL SKETCH

logical map, " The Baltimore Sheet, " published by the United States
Geological Survey. This map, with somewhat extended area, was
republished later in 1892 by Johns Hopkins University as a " Geo-
logical Map of Baltimore and Vicinity " by G. H. Williams and N. H.
Darton.

In July, 1892, Mr. Darton made some progress in mapping the
sedimentary formations of the Gunpowder quadrangle. This trip
was followed by ten days' field work on the Eastern Shore of Mary-
land, mainly for the purpose of investigating the relation of soils to
the peach yellows, the investigation being made at the request of the
United States Department of Agriculture.

During the spring and early summer of 1893 a number of trips
were made to Maryland for additional data for Geologic Atlas folios.
At this time the Magothy formation, which in a portion of eastern
Maryland lies between the Potomac formation and the marine Cre-
taceous sediments, was discriminated. It was defined and described
in a paper entitled " The Magothy Formation of Northeastern Mary-
land. "¹

In the following year some additional observations were made in the
Gunpowder district by Mr. Stanley-Brown.

In 1893-94 Mr. Darton made many observations about Washington
to obtain data for the Washington folio, and some trips were made
into eastern Maryland to obtain photographs to illustrate the final
report.

During the progress of the Coastal Plain work in previous years
much attention had been given to the collection of data regarding
underground water supplies, especially those available for deep wells.
In February, 1894, Mr. Darton presented to the American Institute
of Mining Engineers a short paper entitled " Artesian Well Prospects
in Eastern Virginia, Maryland and Delaware. " ³

In the following year many additional data of artesian and other
deep wells were collected for Maryland and the other states of the
Atlantic Coastal Plain, which afforded the basis for a more elaborate

¹ Am. Jour. Sci., 3d series, vol. xlv, 1893, pp. 407-419, including map.

² Trans. Am. Inst. Min. Eng., vol. xxiv, pp. 372-397, pls. 1-2.