54 HISTORICAL SKETCH

Mr. S. L. Mitchill in " A detailed Narrative of the Earthquakes
of 1811, 1812 and 1813 "¹ describes the phenomena and narrates his
observations in Maryland. He suggests that the effects probably did
not extend northeast of the state line.

In 1817 William Maclure published his classical work on " Obser-
vations on the Geology of the United States of America, with some
remarks on the effect produced on the nature and fertility of soils by
the decomposition of the different classes of rocks. " In this book the
limits and character of the geological formations of Maryland are
described in a broad way.

Samuel L. Mitchill, in a volume dealing with " Cuvier's Essay on
the Theory of the Earth. To which are now added Observations on
the Geology of North America, " and published in New York in 1818,
has numerous references to Maryland geology, especially in the vicinity
of Harper's Ferry, on the eastern shore and in the area about Wash-
ington. The book contains three figures of an elephant's tooth from
Maryland.

Elias Cornelius, ² in an article published in the American Journal
of Science in 1819, refers to the Potomac marble. The same volume
contains a letter to the editor from Dr. Hayden upon " Red Pyroxene
Augite. "

In 1820 Dr. Hayden published in Baltimore a most interesting
volume, entitled " Geological Essays; or an Inquiry into some of the
Geological Phenomena to be found in various parts of America and
elsewhere, " in which numerous Maryland localities are cited, especi-
ally in the vicinity of Baltimore, in support of the theories which he
advanced. Among other interesting facts he mentions the finding of
numerous mastodon teeth in Maryland.

The following year Mr. G. Troost³ announced the discovery of
amber on the Magothy river, Anne Arundel county. In this article
are found descriptive notes regarding its geological occurrence and
the associated minerals and fossils.

¹ Trans. Lit. and Phil. Soc., N. Y., vol. i, 1815, pp. 284-307.

² Vol. i, pp. 214-226.

³ Amer. Jour. Sci., vol. iii, 1821, pp. 8-15.