106 HISTORICAL SKETCH

In July and August, 1887, Mr. McGee traveled along the fall-line
from Washington to New York. For a portion of the distance he
was accompanied by Major J. W. Powell. New data were collected
concerning the distribution and relations of the Potomac and Columbia
formations, the history of river development in the region, and the
nature and origin of the fall-line.

From 1887 to June, 1893, Mr. McGee had leisure only for occa-
sional geological observations in the vicinity of Washington, and these
mainly of transient exposures.

In 1890 he prepared an extended memoir on " The Lafayette For-
mation " for the report of the Director of the Survey. ¹ This memoir
relates mainly to the Southern States, but there are included brief
summaries of the characteristics of the several sedimentary forma-
tions which extend across the Coastal Plain region of Maryland, and a
review of the general geologic history of the province.

In 1888 Professor William B. Clark, of the Johns Hopkins Uni-
versity, was requested to prepare a report upon the Eocene formations
of the United States, and from that time forward devoted consider-
able attention to the Cretaceous and Tertiary deposits of Maryland
and Virginia. ¹

In June, 1889, Mr. N. H. Darton was assigned to work in the
Coastal Plain region in Maryland, District of Columbia and Virginia.
He spent the next five years in almost continuous field work in this
portion of the province. The preliminary work was a reconnaissance
in a boat along the shores of the Potomac, St. Mary's, Patuxent, South,
Severn, Patapsco and Sassafras rivers, and the head of Chesapeake
Bay, with Mr. F. M. Smith as assistant. Then a detailed examination
was made of the East Washington quadrangle, which was mapped in
greater part.

In the spring of 1890 considerable progress was made in mapping
the Coastal Plain formations in the Baltimore quadrangle, on which
the crystalline rocks had been mapped by Dr. G. H. Williams. In

¹ Twelfth Ann. Rept. U. S. Geol. Survey, 1891, pp. 347-521, pls. 32-41.

² Correlation Papers—Eocene. Bull. U. S. Geol. Survey No. 83, 1891, pp.
43-48.