IMPROVEMENTS IN MARINE AND SURVEYING COMPASSES
Year: 1854

page_text: LETTERS PATENT to Alfred Kortright, of James Street, Adelphi, in the
County of Middlesex, Commander in the Royal Navy, for the Invention
PROVISIONAL SPECIFICATION left by the said Alfred Kortright at the
Office of the Commissioners of Patents, with his Petition, on the 4th
August 1854.
I, ALFRED KORTRIGHT, of James Street, Adelphi, in the County of Middle-
5 sex, Commander in the Royal Navy, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN MARINE AND SURVEYING COMPASSES" to be as
follows, namely
This Invention relates to the so arranging mariners' and surveyors' com-
passes, that the deranging influence due to the local attraction ordinarily felt
on board iron ships, or in situations where there are masses of metal in more
or less proximity to the compass, is greatly mitigated or entirely prevented.
In this improved arrangement the needle and index card case is of cast iron.
It is a plain and truly-turned ring, open at the top in the usual manner, and
closed in at the bottom by a glass or other plate, so as to form a box. In
addition to this cast-iron case, rings of external cases of the same metal may
be disposed outside it, so as to produce a still greater protective effect upon
the needle.

page_text: When thus fitted up, the compass needle is no longer subject to the
deranging influence of local attraction.
In constructing my improved compasses, it is preferred to use both light and
heavy needle cards, and it is also preferred to make them with two dipping
needles.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Alfred Kortright in the Great Seal Patent Office on the
3rd February 1855.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALFRED
KORTRIGHT, of James Street, Adelphi, in the County of Middlesex, Com-
mander in the Royal Navy, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Fourth day of August, in the year of our Lord One
thousand eight hundred and fifty-four, in the eighteenth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
Alfred Kortright, Her special licence that I, the said Alfred Kortright, my
executors, administrators, and assigns, or such others as I, the said Alfred
Kortright, my executors, administrators, and assigns, should at any time
agree with, and no others, from time to time and at all times thereafter
during the term therein expressed, should and lawfully might make, use,
exercise, and vend, within the United Kingdom of Great Britain and Ireland,
the Channel Islands, and Isle of Man, an Invention of "IMPROVEMENTS IN
MARINE AND SURVEYING COMPASSES," upon the condition (amongst others) that
I, the said Alfred Kortright, by an instrument in writing under my hand and
scal, should particularly describe and ascertain the nature of the said Inven-
tion, and in what manner the same was to be performed, and cause the same
to be filed in the Great Seal Patent Office within six calendar months next
and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Alfred Kortright, do hereby declare
the nature of the said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement-
This Invention relates to the so arranging mariners' and surveyors' com-
passes, that the deranging influence due to the local attraction ordinarily felt
on board iron ships, or in situations where there are masses of metal in more
or less proximity to the compass, is greatly mitigated or entirely prevented.

page_text: In this improved arrangement the needle and index card case is of cast iron.
It is a plain and truly-turned ring, open at the top in the usual manner, and
closed in at the bottom by a glass or other plate, so as to form a box. In
addition to this cast-iron case, rings of external cases of the same metal may
be disposed outside it, so as to produce a still greater protective effect upon
the needle.
When thus fitted up, the compass needle is no longer subject to the
deranging influence of local attraction.
In constructing my improved compasses, it is preferred to use both light and
heavy needle cards, and it is also preferred to make them with two dipping
needles.
The cast-iron rings or cases may be electrotyped.
I claim the construction of marine and surveying compasses in cast-iron
rings or cases, which rings or cases may or may not be electrotyped.
In witness whereof, I, the said Alfred Kortright, have hereunto set my
hand and seal, this Tenth day of January, in the year of our Lord
1855.
A. KORTRIGHT. (L.B.)