borings on land were mostly core borings, and were generally made with
the chilled shot boring machine.

Base lines, about 2,250 ft. in length, were measured on each side of the
river, and observation points established. It was necessary to build a
triangulation tower 60 ft. high on the New Jersey side as an observation
point. The base lines were measured with 100-ft. steel tapes which were
tested repeatedly, and the work was done at night in order to obtain the
benefit of uniform temperature and freedom from traffic interruptions.
From the base line on the New Jersey side, which passed over the
Weehawken Shaft, an elevated point on the assumed center line on the
side of Bergen Hill was triangulated to, and from this point westward a
closed polygon was measured along the streets to the top of the hill on
the west side and thence along the assumed center line to the portal.
The level transfer across the river was made by sighting across in
opposite directions simultaneously, and also by tide gauges. The outline
of the final triangulation system is shown on Plate VII.

[Illustration: FIG. 2.--(Full page image)

HYDRAULIC SCREWING MACHINE WITH RATCHET DRIVE AND VERTICAL JACK

GENERAL ARRANGEMENT]

[Illustration: FIG. 3.--(Full page image)

HYDRAULIC SCREWING MACHINE WITH RATCHET DRIVE AND VERTICAL JACK

DETAILS]