The Sun.
London, England, 1849-12-31 00:00:00

MARINE LIGHTS.
The Harbour Commissioners and Trinity Board of
Dundee are puzzled to know what to do with the
Tay lights. Since the opening of the railways co-
loured lights have become so common that vessels at
r,
sea may readily mistake the railway signat fgEetbe
marine light, and thus life and property mar)eeelo4i
The Dundee authorities have applied to the Admiralty
for instructions and advice, and it is now perfectly
clear that something must speedily be done to remedy
the evil. A vessel was wrecked in the Tay the other
day, and the captain drowned, from having mistaken
the railway light of Ferry-Port-on-Craig for the
harbour light of Dundee.
But if the harbour trustees of Dundee have felt
themselves called on to take up this matter as one of
the greatest importance to the shipping in-
terest, the Harbour Commissioners of Aberdeen
are still inure imperatively bound to inquire
how the opening of the Aberdeen Railway will affect
our tidal lights. The line of this railway is laid
along the East coast, frc m the Bay of Nigg to Stone
h.lven. The different stations will be signalled with
coloured lights at night, and the ?to] and green being
similar to th red and green of the Aberdeen Har-
bour Lanterns, it need surprise no or.e to hear, onu of
these day s, that a vessel has run ashore at the Cove
or the thy of Nigg. To those who are well
acquainted vvith the coast, the Girdleness light is suf-
ficienl!, in ordinary circumstances, to prevent denger ;
but it is wtll known that many vessels come across
to the East coast, whose elpteins would not know
Girdleness from Kinnaird's Head light, and would
take a coloured light as a guide when a plain light
%could not be seen. At any rate, when we find the
Trinity Board of Dundee alarmed, it is high time
that the subject had engaged the attention of the
harbour authorities of Aberdeen.
fynd happily they have not to go far for a remedy.
The system of tidal lights- and marine signals, in-
vented by our townsman Mr. Rettie, is all that can
be desired. The grand distinguishing feature of
these lights is their distinctive character. Like Mar-
ryatt's signals, they are perfectly unique. That por-
tion of his system which our trustees have adopted is
only a fractional part of his complete whole, with the
difference only of the inversion of the order of the
red for the green. If Mr. Rettie's tidal lights were
universally adopted, there would he perfect safety,
but with the present diversity of lights there is con-
stant danger. This opinion,
,was expressed long be-
fore Mr..Rettie preferred-any 'aim for infringetnetit4Fc"'4l/44e4.'
eme,
of his patent, and we hold by it still, independently
of all considerations affecting that claim-. With us it
is a •vestion of humanity ; and on that ground we
are Aelermined to contend for a distinctive set of
marine lights until they are obtained.—North of
Scotland Gazette.

THE FROGNOSTICATED MGR
TIDE.
Royal Observatory, Greenwich, Dec. 27, 1849.
Gentlemen, —ln reply to your letter of yesterdly,-;-:
I have to state that I bad not previously seen thee::
`letter, of which you enclosed a copy, although I had'
.hearts thtsta rumour on the probability of a large tidv.
,'
an the 29th or 30th inst was now current. 4

There is no foundation whatever for such a rumour.
The circumstances on which the magnitude of the
tide depends are mainly these three !-
The tide is high when the moon ialig; it Is high
when the moon is in perigee,ind it is Wier when the
moon is in the equator. (I omit LH tantidOWPF the
sun's distance, because the effect of its ye*tioia. is
practically quite insignificant.)
The largest tides usually occur on the day nett
following the states of the moon which I h tve men-
tioned.

Two of these circumstances occur on the 29th
(namely, the moon will be full and in perigee). But
the moon instead of being in the equator, will be t
her greatest north declination ; and this circumstai e 3
will reduce the tide considerably.
The three increasing circumstances which I have
mentioned have repeatedly been combined in late
years, all tending to increase the tide ; and yet no
mischief has been done.
I am, Gentlemen, your obedient selyan'.
G. B. Amy..
Messrs. Scott and Hopkins, Times' Off uth