Improvements in Magnetic Compasses.
Year: 1890

page_text: Date of Application, 21st July, 1890-Accepted, 13th Sept., 1890
COMPLETE SPECIFICATION.
[Communicated from abroad by ROBERT STANTON DIXON, of Sydney, in the Colony
of New South Wales, Mariner.]
Improvements in Magnetic Compasses.
I, HENRY EDWARD NEWTON of the Office for Patents, 6 Bream's Buildings,
Chancery Lane, in the County of Middlesex, Patent Agent, do hereby declare the
nature of this invention and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement :-
The invention consists essentially of two parts, a vacuum jacket, and a vacuum
cover or shield, so disposed around the magnetic needle, that while the latter shall be
susceptible to the carth's magnetism, local magnetic influences shall have but little
or no effect upon it. But in order that the invention may be better understood,
reference will be made to the accompanying sheet of drawings, in which
Fig. 1 is a vertical section of the invention as applied to a mariner's compass.
Fig. 2 is a plan view of the same.
Fig. 3 is a detail section, on an enlarged scale, of the vacuum cover or shield
attached to a magnetic needle.
The vacuum jacket consists of two bowls A1, A2, of different diameters, the smaller
being placed within the larger, and secured together in such a way as to render it
possible to establish or create a vacuum in the space A between the two bowls A1, A2
A cock a is placed in any suitable position on the jacket (see Fig. 1), through which
the space A is exhausted of air, and the vacuum thus created permanently maintained.
The magnetic needle B, is mounted within a bowl C, which is swung in gimbals c
in the usual manner, but within the jacket.
Placed above the magnetic needle B, and in this instance secured to it in any
suitable manner (see Fig. 5) is a hollow shield or cover D, that is preferably
constructed of circular form, so that its upper surface may be graduated as a compass
card (see Fig. 2).
In the drawing, the hollow shield D) is shewn as a very flat or squat cone, at the
apex of which is placed a suitable cock d, through which the space d' within the
shell of the shield may be exhausted of air, and the vacuum thus created be
permanently maintained."
The shell of this shield D may, if necessary, be strengthened, so as to enable it the
better to support the atmospheric pressure. This may be effected either by internal
stays, by corrugating the shell, or in any other practical manner.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me
from abroad, I declare that what I claim is:
1. Mounting a magnetic compass, within a vacuum jacket such as that herein
described, and as illustrated in the accompanying drawing.
2. The vacuum shield or cover D, in combination with the magnetic needle, B, of
a magnetic compass.
3. The combination with a magnetic compass, of the vacuum jacket A¹ A², and the
vacuum shield or cover D, for the purpose of rendering the magnetic needle B, less
susceptible to the influences of local magnetism.
Dated this 21st day of July 1890.
NEWTON & SON,
Agents for the Applicant.