MARYLAND GEOLOGICAL SURVEY 121

ends of lines were determined by the plane-table. Principal lines of
soundings were run parallel to the meridian. Cross or check lines
intersected them at right angles. Lines of levels were run between
the tide gauges at Henderson's, Bollman's and Woodall's, but no appre-
ciable differences of plane were found. The same result was obtained
by simultaneous observation of tide at the several stations mentioned.

This, the most thorough and elaborate survey hitherto made in and
adjacent to the harbor of Baltimore, is represented by five topographic
and five hydrographic sheets.

In March, 1881, Mr. Charles Junken, United States Coast and
Geodetic Survey, made a re-survey of that part of the Patapsco lying
between Fort Carroll and the line of Marine Hospital Lazaretto.

SURVEY OF 1886. —In June, 1886, at the request of Major N. H.
Hutton, Engineer of the Harbor Board, the work of 1876 was sup-
plemented by a verification of the triangulation and its adjustment
to more recent computations made by the Computing Division of the
Coast and Geodetic Survey Office of the triangulation of the Chesa-
peake Bay. The purpose of Major Button's request, however, was
the tracing upon the ground of the Port Warden line established by
the Commission of 1876 and its connection with the triangulation in
such a way that its identification could be secured by reference to
established ground-marks. The Superintendent of the Coast and
Geodetic Survey assigned to this work Assistant O. H. Tittmann.
Copies of the original plane-table sheets of the special survey of 1876
were in possession of the Harbor Board of Baltimore, and upon these
were laid down the Port Warden line of the harbor after due con-
sultation with the engineer of the Board. In conformity with the
suggestions of Major Hutton, Mr. Tittmann confined that part of his
work to tracing the pier-head lines around the harbor—the bulk-head
lines in certain places only being marked.

The method pursued was to transfer the Port Warden line to the
original sheets. These sheets were then taken into the field, and in
general the points of deflection of these lines were identified by means
of the plane-table. They were then referred by distance measure-
ments and deflection angles to stones planted in the streets or side-