IM- PROVEMENTS IN MARINERS' COMPASSES
Year: 1876

page_text: LETTERS PATENT to William Robert Lake, of the Firm Haseltine, Lake, & Co.,
Patent Agents, Southampton Buildings, London, for the Invention of "IM-
PROVEMENTS IN MARINERS' COMPASSES." A communication from abroad by
Silas Bent, of St. Louis, Missouri, United States of America, late Lieutenant in
the United States Navy.
ealed the 7th April 1876, and dated the 16th February 1876.
COMPLETE SPECIFICATION filed by the said William Robert Lake at the
Office of the Commissioners of Patents on the 16th February 1876.
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co, Patent Agents,
Southampton Buildings, London. "IMPROVEMENTS IN MARINERS' COMPASSES." A
communication from abroad by Silas Bent, of St. Louis, Missouri, United States*
of America, late Lieutenant in the United States Navy.
In using a compass allowance must be made for the variation of its needle from
the true north point. To the mariner especially it is important that this variation
be properly allowed. If improperly allowed an error of double the variation is
made, and when approaching land or in intricate seas this is a fruitful source of
disaster to vessels.
· Hitherto it has been customary for the navigator to use a compass whose card
is permanently attached to the needle, rendering it necessary to make the needful
correction mentally and as often as the variation is applied. This mental process
is not only annoying, but it is so unreliable that no navigator even the most.
experienced is free from the dangerous mistakes it involves.
This Invention is designed to obviate these difficulties and to furnish a compass
which in its mechanical arrangement is such that by a simple manual process
the variation of the magnetic needle may be applied directly to the compass by
even the most uneducated seaman, so that until a change occurs in the variation
the courses steered will be the true courses, the winds recorded will be the true
winds, the bearings taken will be the true bearings, and no allowance or correction
for variation whatever will be required when working up the dead reckoning, and
above all that in shaping courses the true bearings given by the chart are the
courses to be sailed.

page_text: DESCRIPTION OF THE DRAWING,
Figure 1 represents in vertical cross section the screw used in attaching the card
to the needle.
Figure 2 is a top view of the needle.
Figure 3 is a side elevation of the said needle.
And, Figure 4 is a plan showing the said needle adjusted to a variation of
20° west.
Like letters indicate the same parts throughout the Drawing.
A represents the preferable form of the magnetic needle used, and B the card.
The latter is of the ordinary kind. The needle in length corresponds with the
diameter of the card, and at either end or pole is provided with pointers respectively
lettered N and S. The pointers are of suitable inaterial and as shown in Figures
2, 3, and 4, extend upwardly and preferably inwardly so as when in position to
overlap the graduated edge of the card. To readily distinguish the pointers that at
the north pole N is sharpened, while the one at the south pole S is broadened.
C, Figures 1 and 4 represents the usual jewelled nut constituting the support for
the needle, which is preferably used to attach the card to the needle at any desired
adjustment. In operation the card and needle are relatively adjusted by bringing
the north pole of the needle to the right or left of the north point of the card, until
the pointer N is at the degree or fraction thereof that the variation is known to be
east or west of the true meridians at that locality: The card and needlë arë thën
fixed in that relative position; thus adjusting them so that whilst the nortli and
south points of the card will indicate the true meridian the needle will lie in the
direction of the magnetic meridian (or in that direction which is the resultant of
the combined application of both the terrestrial and the local variations.
In Figure 4 the adjustment is to a variation of 20° west. The compass is
readjusted with every change in the variation.
The conspicuousness given to the indicating points at the extremities of the
needle enables any one to determine by a glance in the binnacle whether or not
the variation has been properly applied.
Having thus fully described the said Invention as communicated to ime by my
foreign correspondent, and the manner of performing the same I wish it understood
that I claim,
First. The combination of the magnetic needle provided with the pointer, the
card, and the nut, as above specified and for the purpose set forth.
Second. The combination of the magnetic needle provided with the north and
south points, the card, and the nut, as above specified and for the purpose set
forth.
Third. The combination in a_mariners' compass of a suitable securing device with
a card and needle which are relatively adjustable, as above specified and for the
purpose set forth:
In witness whereof, I, the said William. Robert Lake, have hereunto set, my
hand and seal, this Sixteenth day of February, in the year of our Lord
One thousand eight hundred and seventy-six.
Witness,
ROWLAND GEORGE BROWN,
8, Southampton Bdgs.,
London.
W: ROBT. LAKE; (L.S:)