the streets along the tunnel lines. Angle readings were repeated many
times, as is usual in such work. Fig. 1 shows the triangulation, the
street measurements being omitted.

Levels were first transmitted across the river by simultaneous
observations of the river surface; then by several repetitions, across
Blackwell's Island and the narrow channels on each side, where the
longest sights were about 1100 ft.; and, finally, by several lines
through the tunnel of the East River Gas Company at 71st Street.

The franchise granted by the City of New York provided for the sale to
the Railroad Company of the portions of 32d Street between Seventh and
Eighth Avenues, and between Eighth and Ninth Avenues. Later, the Company
acquired by purchase the portion of 32d Street between Ninth and Tenth
Avenues. The franchise granted sub-surface rights under streets around
the station site to within 19 ft. of the street surface under Seventh,
Eighth, and Ninth Avenues; to within 30 in. of the street surface under
31st and 33d Streets, except that, under the sidewalks opposite the
station, that is to say, the south sidewalk in 31st Street and the north
sidewalk in 33d Street, the construction must be at least 5 ft. below
the street surface. In carrying out the work, full use of these rights
was made under Eighth Avenue, but only under such portions of Seventh
and Ninth Avenues as were indispensable for access by trains to the
station area. It was not practicable to make full use of the rights
granted under 31st and 33d Streets without incurring great expense for
supporting adjacent buildings or for injuries to them, and, after
careful consideration, the arrangement shown in the plans was decided
on, making about 45% of the sub-surface area under these streets
available at track level.