An Improvement relating to Magnetic Compasses.
Year: 1896

page_text: Date of Application, 27th July, 1846
Complete Specification Left, 26th Apr., 1897-Accepted, 19th June, 1997
PROVISIONAL SPECIFICATION.
An Improvement relating to Magnetic Compasses.
I, JOSEPH DANIEL ROWBOTHAM BLAIN, of 7 Rushmore Road, Lower Clapton,
County of London, Engineer, do hereby declare the nature of this invention to be
as follows:-
Instead of the ordinary pencil or like magnets being fitted in a compass bowl or
box, I construct and employ a hollow sphere composed of sections separately
magnetized and having all the like poles congregated.
The sphere when mounted upon pivots has free motion to adjust itself due north
and south without regard to the outside magnetic influence.
The sphere may have a pointer or finger for the reading of the card.
H. GARDNER,
Patent Agent, 166 Fleet Street, London,
Agent for the said J. D. R. Blain.
I, JOSEPH DANIEL ROWBOTHAM BLAIN, of 7 Rushmore Road, Lower Clapton,
County of London, Engineer, 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 hereafter described is based upon the following features:-The lines
of force round a bar magnet form themselves into a sphere, the axis of which is
formed by the bar itself. Such a magnet freely suspended will take up a north and
south direction.
It will be found that any influence that would tend to disarrange the spherical
character of those lines, will also move it out of its conformity to the magnetic
meridian, but a compound magnet constructed on my new principle may be described
as an ironclad magnet, or as one whose lines of force are garrisoned and protected.
Again such a magnet exerts its greatest force internally or between its poles and
is saved from the danger to which the bar magnet is exposed of exerting the maximum
of attraction toward external objects and being in its turn attracted by them.
Instead of the ordinary pencil or like magnets being fitted in a compass bowl or
box, I construct and employ a hollow -sphere composed of sections separately
magnetized and having all the like poles congregated.
The sphere when mounted upon pivots has free motion to adjust itself north and
south without regard to the outside magnetic influence.
The sphere may have a pointer or finger for the reading of the card.
My construction of compass will be understood by reference to the annexed
drawings.

page_text: Figure 1 section or division line of two of the four parts constituting a sphere as
indicated at Figure 4.
Figures 2 and 3 indicate the inside of two sections of the sphere to show that
the sections coincide with each other and form a hollow bulb when united along their
meeting edges a, a, and along the enlarged surfaces b, b.
The sections are magnetized separately and all the similarly magnetized points
brought together.
Before uniting the sections, I place a bridge c with a jewelled centre for the pivot
point of a rod d when the bulb is placed over the rod there being a hole e in the
bottom section to allow of play or oscillations.
The bulb carries a card f as at Figures 4 and. 5, which represent a side elevation
and a plan view respectively of the complete compass.
The hollow spherical bulb constituting my improved compass may be prepared by
varnish in the usual manner for immersion in a liquid compass bowl, or it inay be used
in a dry bowl of a binnacle as desired.
Among the advantages obtained by this improved magnetic compass
1. It can be more easily adjusted, the induction from the metal of the vessel not
seriously affecting it.
2. It will not be so much subject to dip in either hemisphere, as an ordinary
compass.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
The construction of a hollow bulbous magnet built up of sections and having
increased ends internally arranged and in touch with each other, as and for the
purposes set forth and substantially as represented in the annexed drawings.
H. GARDNER,
Patent Agent, 166 Fleet Street, London,
Agent for the said J. D. R. Blain.
H. GARDNER,
Patent Agent, 166 Fleet Street, London,
Agent for the said J. D. R. Blain.