MARYLAND GEOLOGICAL SURVEY 113

Maryland began in 1891, when a study of the Potomac river was
commenced, the investigations being carried on by Mr. Cyrus C. Babb,
under the direction of Mr. F. H. Newell, the Chief Hydrographer of
the Survey. Observations of river height were first made at Chain
Bridge, about 3 miles above the city of Washington, and at later times
reconnaissance and discharge measurements were made on some of the
higher branches in order to obtain data of run-off from the catchment
areas of different character under similar climatic conditions.

Later the matter was given more careful attention and preparations
were made for a thorough series of measurements. A number of
stations were established along the line of the river, viz., at Point of
Rocks, Great Cacapon and Cumberland. Preparatory to this work
at each of these points, apparatus for registering the heights of the
water was established, and careful records have been kept since that
time.

Use has also been made of the daily record kept since 1878, by the
officials of the Washington Aqueduct, of the height of the water flow-
ing over their dams at Great Falls.

Simultaneously with the gauge height records at Great Falls,
another record has been kept, viz., condition of water, as it is called,
or observations on the amount of matter carried in suspension in the
river.

Several stations upon other streams were established during the
year 1896 in co-operation with the Maryland State Weather Service,
viz., at a point four miles northeast of Frederick on the Monocacy
river, at Laurel on the Patuxent river, near Woodstock on the Patapsco
river and at Rowlandville on Octararo creek. It is planned to extend
this work in the near future.

STATISTICAL WORK.

An annual tabulation of the mineral resources of the United States
in which Maryland appears, was undertaken by the United States
Geological Survey in 1882, the first report by Albert Williams, Jr., be-
ing published in 1883. Since 1886 this work has been under the direc-
tion of Dr. David T. Day, who has published annual reports regarding