value as well, and that the
pressure was very far from 7,000 lb., in all probability, at the
beginning of the test.

In the case of the California stove-pipe wells driven by the Board of
Water Supply on Long Island, the writer is informed that one of these
tubes, 12 in. in diameter, was sunk to a depth of 850 ft. In doing this
work the pile was excavated below the footing with a sand pump and was
then sunk by hydraulic pressure. Assuming the maximum capacity of the
jacks at 100 tons, which is not probable, the skin friction could not
have amounted to more than 75 lb. per sq. ft. It cannot be assumed in
this case that the excavation of the material below the pile relieved
the skin itself of some of its friction, as the operation consumed more
than 6 weeks, and, even if excess material was removed, it is certain
that a large percentage of it would have had time to adjust itself
before the operation was completed.

[Illustration: PLATE XXIX, FIG. 1.--A 14-GAUGE, 14-IN., HOLLOW
(NON-TELESCOPIC), CALIFORNIA STOVE-PIPE PILE WHICH MET IMPENETRABLE
MATERIAL.]

[Illustration: PLATE XXIX, FIG. 2.--CHENOWETH PILE, PENETRATING HARD
MATERIAL.]

In connection with this, the writer may call attention to the fact that
piles driven in silt along the North River, and in soft material at
other places, are sometimes 90 ft. in length, and even then do not offer
sufficient resistance to be depended on for loading. This is due to the
fact that the end of the pile does not bear in good material.

The relation between bearing value and skin friction on a pile, where
the end bearing is in good material, is well shown by a case where a
wooden pile[G] struck solid material, was distorted under the continual
blows of the hammer, and was afterward exposed. It is also shown in the
case of a 14-in. California stove-pipe pile, No. 14 gauge, the point of
which met firm material. The result, as shown by Fig. 1, Plate XXIX,
speaks for itself. Fig. 2, Plate XXIX, shows a Chenoweth pile which was
an experimental one driven by its designer. This pile, after getting
into hard material, was subjected to the blow of a 4,000-lb. hammer
falling the full length of the pile-driver, and the only result was to
shatter the head of the pile, and not cause further penetration. Mr.
Chenoweth has stated to the writer that he has found material so compact
that it could not be penetrated with a solid pile--either with or
without jetting--which is in line with the wri