MARYLAND GEOLOGICAL SURVEY 81

ing the matter, in which much information is given concerning old
maps and charts that deal with the physiography of the state. ¹

The proposed extension of the Chesapeake and Ohio Canal to the
Ohio river led to the preparation of a report² to Congress about the
same time in which a discussion of the country between Cumberland
and Pittsburg is found.

An interesting contribution was made in 1875 by Dr. Christopher
Johnston of Baltimore " About the rediscovery of the 'Bermuda
Tripoli' near Nottingham, on the Patuxent, Prince George's County,
Md. "³

In 1878 Professor J. J. Stevenson published two articles dealing
mainly with the geology of southwestern Pennsylvania, in which
western Maryland is included. In the first⁴ of these articles the sur-
face features of the region are considered, and in the second⁵ the
Devonian rocks.

Scharf's " History of Maryland, " which appeared in 1879, con-
tains many references to the early maps, history and industries of the
state, and has especial value on account of the accessibility of the
volumes.

The discovery of Butrotrephis flexuosa in the Peach Bottom slate
in 1879 and its determination by Lesquereux led to the publication
of two articles by Professor J. P. Lesley in 1880 " dealing with the age
of the rocks. During the same year Professor Heilprin of Philadel-
phia published the first of his contributions upon the Tertiary fauna of
Maryland, in which he discusses the " Stratigraphical Evidence
afforded by the Tertiary Fossils of the Peninsula of Maryland. "⁷

Scharf's " History of Baltimore City and County, " which appeared
in 1881, contains an account of the topography and geology of the.

¹ See especially " Report and accompanying documents of the Virginia
Commissioners appointed to ascertain the Boundary Line between Maryland
and Virginia. " Richmond, 1873.

² House Doc. No. 208, 43rd Congress, 1st session, 59 pp., 1874.
³ Proc. Boston Soc. Nat. Hist., vol. xvii, 1875, pp. 127-129.

⁴ Amer. Jour. Sci., 3 ser., vol. xv, 1878, pp. 245-250.

⁵ Amer. Jour. Sci., 3 ser., vol. xv, 1878, pp. 423-430.

⁶ Proc. Amer. Phil. Soc., vol. xviii, 1880, pp. 364-369. Amer. Jour. Sci.,
3 ser., vol. xix, 1880, pp. 71-72.

⁷ Proc. Acad. Nat. Sci., Phila., vol. xxxii, 1880, pp. 20-33.