tunnels east of the Terminal Station the ruling grade is 1.5% for both
east-bound and west-bound traffic. There is, however, descending with
the traffic, a short section on a grade of 1.9 per cent. These grades
would be objectionable with steam locomotives under a heavy traffic, but
the development of the electric locomotive has rendered possible the
operation of grades which would have formerly been considered
prohibitive.

From the junction with the Pennsylvania Railroad, near Harrison, N. J.,
to Woodside, Long Island, a distance of 13.66 miles, there is an average
of 1.5 curves per mile; the line having a total curvature of 230
degrees. The maximum curvature is 2 degrees.

[Illustration: PLATE III.--P. T. & T. R. R. East River Division.
Sunnyside Yard]

_Method of Construction of Sub-River Tunnels._--The character of the
material through which the tunnels were to be constructed differed
greatly in the two rivers. The bed of the North River, at the level of
the tunnels, consists of silt composed principally of clay, sand, and
water, while that of the East River is formed of a great variety of
materials, such as quicksand, sand, boulders, gravel, clay, and
bed-rock. When the method of construction had to be decided there were
no thoroughly satisfactory precedents to follow in the case of either
river, although the Gas Tunnel under the East River, the partly
constructed Hudson Tunnels under the North River, the St. Clair Tunnel
under the St. Clair River, the Blackwall and several other tunnels under
the Thames River at London, supplied much useful information. The
smaller tunnels for a lighter traffic, since so successfully constructed
under the North and East Rivers, had not then been completed. Under