IMPROVEMENT IN MAGNETIC COMPASSES
Year: 1885

page_text: PROVISIONAL SPECIFICATION.
I, ALEXANDER MELVILLE CLARK, of the firm of A. M. and Wm. Clark, of
53, Chancery Lane, in the County of Middlesex, Fellow of the Institute of Patent
Agents, do hereby declare the nature of the said Invention for AN IMPROVEMENT
IN MAGNETIC COMPASSES, a communication to me from abroad by Messrs Favi,
Paride and Company of Ferrara in the Kingdom of Italy, Scientific Instrument
Makers, to be as follows:-
This Invention relates to an improvement in magnetic compasses and has for its
object to protect the magnetic needle from disturbing influences especially that
due to the presence of iron in the vicinity, this disturbing influence being so
powerful, owing to the large amount of iron in the construction of a ship and the
great number of articles of iron on board, as to sometimes cause the ucedle to
deviate as much as 70° from its true position.
According to the present Invention, instead of avoiding the use of iron as
hitherto, this metal is made to enter exclusively into the construction of the compass
whereby the magnetic force is concentrated. According to this invention the
compass box is made of cast iron, the card of sheet iron and the gimbals of wrought
iron. The construction of the compass is the same as in ordinary and differs only
in the metal of which it is constructed, the rings, box, bearings &c being all made.
of wrought or cast iron in suitable proportion, with the object more especially in
the case of iron vessels of neutralizing the local attraction of the iron of which they
are constructed and of concentrating this magnetic force in the compass, whereby
the needle is rendered no longer liable to deviation.
:

page_text: COMILLIE
I, ALEXANDER MELVILLE CLARK, of the firm of A. M. and Wm. Clark, of
53, Chancery Lane, 'in the County of Middlesex, Fellow of the Institute of Patent
Agents, do hereby declare the nature of the said Invention for AN IMPROVEMENT
IN MAGNETIC COMPASSES (a communication to me from abroad by Messrs Favi,
Paride and Company of Ferrara in the Kingdom of Italy Scientific Instrument
Makers) and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
This Invention relates to an improvement in magnetic compasses and has for
its object to protect the magnetic needle from disturbing influences especially that
due to the presence of iron in the vicinity, this disturbing influence. being so
. powerful, owing to the large amount of iron in the construction of a ship and the
great number of articles of iron on board as to sometimes cause the needle to
deviate as much as 70° from its true position.
According to the present Invention instead of avoiding the use of iron as hitherto,
this metal is made to enter exclusively into the construction of the compass
whereby the magnetic force is concentrated.
The invention is illustrated by way of example in the accompanying drawing
figure 1 of which represents a perspective view of the compass. Figure 2 is a
vertical section taken through the centre of the compass box and gimbal and
figure 3 is a plan.
The compass consists essentially of a cast iron box B provided with a compass
card E of sheet iron and at the centre of which is pivoted the magnetic needle.
The compass box is pivoted in a wrought iron ring or gimbal C which is in turn
pivoted at right angles in a support D also of wrought iron.
The construction of the compass is the same as in ordinary and differs only in
the metal of which it is composed, the rings, box, bearings pivots & being all made
of wrought or cast iron in suitable proportion, with the object, more especially in
the case of iron vessels of neutralizing the local attraction of the iron of which they
are constructed and of concentrating this magnetic force in the compass whereby
the needle is rendered no longer liable to deviation.
Having now particularly described and ascertained the nature of the said
Invention and in what manner the same is to be performed I declare that what
I claim is
A compass in which the box and other parts composing it are made of wrought
iron cast iron or other metal which by its powers of attraction will shield the
magnetic needle from the disturbing influences of metal in its vicinity as
specified.