The lighthouse is furnished with an anemometer and tidal
gauge; and its appointments are altogether of the most complete
description. It is chiefly, however, with regard to the system adopted
in the lighting arrangements that novelty presents itself.
The main object, in the instance of a light placed as a beacon to warn
mariners of their proximity to a dangerous coast, is to obtain the
greatest possible intensity and amount of penetrating power. A naked or
simple light is therefore seldom, if ever employed; but whether it
proceed from the combustion of oil or gas, it is equally necessary that
it should be combined with some arrangement of optical apparatus, in
order that the rays emitted may be collected, and projected in such a
direction as to render them available to the object in view; and in all
cases a highly-polished metal surface is employed as a reflector.
[Illustration: HARTLEPOOL LIGHTHOUSE.]
In the Hartlepool Lighthouse the illuminative medium is _gas_. The
optical apparatus embraces three-fourths of the circumference of the
circle which encloses the light, and the whole of the rays emanating
from that part of the light opposed to the optical arrangement are
reflected or refracted (as the case may be), so that they are projected
from the lighthouse in such a direction as to be visible from the
surface of the ocean.
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