EXPLANATION OF TERMS USED 7
carriage, which is diawn up an inclined plane, called a
Slipway, into the chamber from which the tidal water is
excluded by means of a pair of gates. As only vessels
of the smaller class are suitable for slipway traction, slip
docks are not very important, nor are they very numerous,
since the slipway itself is adaptable to carrying out of
repairs when its length is sufficient to bring the vessel
beyond the range of tidal influence.

In America, the term Slip is applied to the area of
water lying between two piers, or ““ docks.”

We now proceed to deal with another set of expressions
in common use, with divergent meanings and anomalous
applications.

JETTIES, WHARVES, AND PIERS

Jetty, Pier, and Wharf are terms used in many cases so
indiscriminately, that it is difficult to differentiate them.
But there is a difference, and to make matters clear for the
student, we may, perhaps elaborate a little. The root
notion of a jetty is something which juts out or forward.
Its use, therefore, should be limited at ports to structures
which jut out from the general shore, or river, line into the
sea or waterway. This at once brings us into conflict with
American terminology, in which such a structure would be
called a dock, though the term pier is also common. In
its association with building construction, a pier is entitled
to be described as a kind of detached member or offshoot
from a main structure, but the underlying idea seems to be
that of affording support, as in the piers of a bridge. In
marine works, however, it is the sense of detachment which
is uppermost, and, in this respect, it very largely corres-
ponds with the basic idea of the word jetty. In some
quarters, its application is to a landing stage for passengers,
but, even then, the idea of detachment is justified, since
many such landing stages jut out into a river or the sea.

We are, perhaps, compelled by general use to accept the
terms pier and jetty as substantially interchangeable,

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