| The series
of photographs taken on August 16 (this photo), September 13 (B16736),
and October 11, 1910 (B16849) document the excavation of the basements
of the new Bankers Trust Building. At the center of the photo a team of
horses and cart wait below what is probably a hopper used to store spoil
excavated from the foundation hole. A similar hopper, with a wood gate
at the end of along wood lever, is visible to the left in the photo. The
two rectangular structures at the north side of Wall Street may be caissons.
The steel sheet piling, which had been delivered to the site in July,
can be seen at the short ends of the caissons. The steel sections would
have increased the strength of the caissons, but were probably placed
at the ends of the boxes to provide a key between one section of foundation
wall and the next. The space between the caissons that are visible in
the photo has probably been previously excavated and filled with reinforced
concrete. The heavy steel section visible in the caisson nearest the intersection
of Wall and Nassau Streets and just west of the other caisson may be part
of the connection between the concrete foundation and the steel frame
superstructure. A third steel section may be concealed by the temporary
drive between Wall Street and the excavation. While caissons used on land
(as opposed to those under water) do not need to be sealed on their upper
end, the boards across the top of the taller of the two caissons on Wall
Street have probably been installed to provide protection to the mechanics
excavating at the bottom of the caisson. The cylinder at the center of
the caisson may have been a shaft used for removing spoil from the bottom
of the caisson or may be a sleeve used to guide insertion of the steel
section.
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