An Account of the Bell Rock Light-House: Including the Details of the Erection and Peculiar Structure of That Edifice; to Which Is Prefixed a Historical View of the Institution and Progress of the Northern Light-HousesStevenson, Robert
History
An Account of the Bell Rock Light-House: Including the Details of the Erection and Peculiar Structure of That Edifice; to Which Is Prefixed a Historical View of the Institution and Progress of the Northern Light-Houses
Stevenson, Robert
Bell Rock Lighthouse (Scotland); Lighthouses -- Scotland
A curious anomaly connected with the flowing and ebbing of the sea, in
the early part of each tide, is observable in the contrary currents
which take place along the shore, and at a distance from it. For
example, the flood-tide begins to flow in many situations two or even
three hours sooner on the shore than at the distance of from one
mile to four miles in the offing. The same thing also happens with
regard to the ebb-tide, which begins to fall and run in a contrary
direction to the flood-tide, two or three hours sooner on the shore
than at a distance. These effects are very different from the state of
things three or four leagues from the land, or in the open sea, where
the lateral motion of the tide-waters is scarcely sensible. That an
extensive tract of coast should produce changes on the current of the
tides, is perhaps what we should expect; but it is somewhat curious
to find the same appearances connected with small islets, and, as in
the case of the Bell Rock, even with an insulated reef, situate at the
distance of 12 miles from the land, and sunk to the depth of from 2 to
3 fathoms under the surface of high-water. So strikingly observable is
this, that the tide begins to ebb about two hours sooner on the Bell
Rock than at the short distance of one mile from it. In the course of
the light-house operations this was rendered sufficiently obvious, by
the swinging round of the several vessels at their moorings according
to the flood and ebb tides. For example, the Floating Light-ship was
moored about three miles in a north-west direction from the Bell
Rock, and the moorings of the Tender and two Stone Lighters, were
respectively laid down at the distance of ¾ and ½ mile from it, as
will be seen from Plate V. Now, these vessels were all found to swing
to the tide at periods proportional to their distance from the rock.
Although it may, therefore, seem strange, that this comparatively small
object should affect the tides in its vicinity in a manner similar to
the shores of an extensive coast; yet, as the rock shelves outwards,
with an extensive base, especially on the northern side, it must impede
the under current of the tide, and indeed forcibly proves the existence
of such under currents.
[Sidenote: Not accounted for by Writers on the subject.]
Public-domain text, read in full here on John Shaqi.
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