AN IMPROVED COMBINED CLINOMETER AND PRISMATIC COMPASS
Year: 1881

page_text: LETTERS PATENT to Francis Barker, of Clerkenwell, in the County of
Middlesex, for an Invention of "AN IMPROVED COMBINED CLINOMETER AND
PRISMATIC COMPASS."
PROVISIONAL SPECIFICATION left by the said Francis Barker at the Office
of the Commissioners of Patents on the 4th May 1881.
+
FRANCIS BARKER, of Clerkenwell, in the County of Middlesex. "AN IMPROVED
COMBINED CLINOMETER AND PRISMATIC COMPASS."
My Invention relates to an improved combined prismatic compass and
clinometer.
.
In such instruments as heretofore made the clinometer disc or card and compass
card have usually been placed back to back in the same case, and it has been
necessary to make the prism and sights detachable, and to shift or adjust them for
use in connection with the one or other face of the instrument. This adjustment
is troublesome and a cause of error, and involves a loss of time which might be of
moment during military operations.
According to my Invention I obviate these objections, and produce a more.
convenient and less bulky instrument having a single face only by mounting the
compass card beneath the clinometer disc or card, and facing in the same direction
a segment of the clinometer disc being cut away to admit of the compass card
being seen, the fonner being held stationary with this opening opposite the prism
when the compass is in use. The sights are not detachable, but the prism is
capable of adjustment to focus it either for the compass or clinometer. The disc
of the latter may have the centre cut away to allow the centre of the compass card
to be seen, leaving only a rim or ring having a segment cut away, and cross arms
for mounting it on its pivot.

page_text: Figure 1 is a plan or face view of my improved combined instrument, the top or
cover of the case being removed; Figure 2 is a central section of the same taken
on line 1-1 Figure 1; Figure 3 is an underside view of the clinometer card and
cover of the instrument removed to show the way the clinometer card is mounted ;
Figure 4 is a face view of the clinometer card (shown in Figure 1) separately;
Figure 5 is a face view of a clinometer card with the centre part cut out.
A is the metal case constructed as usual in prismatic compasses, the top cover A¹
being flanged to fit on the body of the case with a rebated joint, and having a
segmental glazed opening, indicated by dotted lines a, a, opposite the prism, and
a circular opening a, a, also indicated by dotted lines. It is likewise provided
with a flat side or base A2 for application to a plane surface as usual in clinometers;
B is the usual prism and front sight, and C is the usual back sight or vane of a
prismatic compass; D is the clinometer disc or card, and M is the magnetic compass
card mounted on a centre fixed to the back of the case in the usual manner; both
these cards face in the same direction. The clinometer card D is a metal disc
having a segment equal to nearly one fourth its circumference cut away to admit
of the compass card being seen. It is mounted on a centre turning in the cover
of the case, and in a cross bar d fixed at the ends to the sides of the cover, the
disc D turning between the two, as shown in Figures 2 and 3. The disc D is
suitably graduated for the purpose of a clinometer, and has a weight e attached to
it at back in such a position that the zero upon its face (which should be at least
90° from the edge of the segmental opening in the disc) will be opposite the prism
when the disc is vertical, and the prism and vane are in the same horizontal plane;
f is a stud carried by cross bar d, against which the weight e or any other projection

page_text: on disc D comes, in order to stop the disc readily with the opening in it opposite.
to the prism. The disc Dis held in this position when not in use by pushing
inwards a sliding bar g terminating in a fork, which embraces a central boss h fixed
to the back of disc D and holds it stationary. The prism B is made adjustable, as
shown in dotted lines in Figure 2, in the usual manner and to a sufficient extent
to enable the prism to be focussed either for viewing D or M.
In Figure 5 the clinometer card is a mere ring of metal with a cross bar for
mounting it on its pivot. The ring is graduated on its inner edge, the graduations
on the compass card beneath being made upon circles corresponding in diameter to
those of the clinometer, so as to lie immediately below them and be viewed without
adjusting the prism otherwise than to focus it. The ring is cut away slightly on
the inner edge at i, to permit of the compass card being seen through the prism.
I would observe that it is not absolutely necessary, although decidedly preferable,
to have an opening in the clinometer card to admit of viewing the compass card.
The two cards may be mounted the one above the other and face in the same
direction, so as to be viewed with the same prism and sights without readjustment
(except for focussing), even though the clinometer card is an entire disc. This may
be accomplished by moving the clinometer card out of the way in order to view
the compass card, and this may be done either by hinging the cover to the case at
one side, so that it may be raised like the lid of a watch (carrying with it the
clinometer card) for using the compass; or the cover and clinometer card may be
wholly removed from the case for the same purpose, but this is undesirable as it is
liable to be lost. In either case the clinometer card would be mounted in the cover
as before described. Or the clinometer card may be so much smaller in diameter
than the compass card that the graduations of the latter are visible around it with-
out removal, but in this case an ordinary sight would have to be used instead of a
prism.
Having described the nature of my Invention, and the manner of performing the
same, I declare that what I claim as my Invention to be protected by the herein-
before in part recited Letters Patent is,―
1st. A combined compass and clinometer in which the two discs or cards are
mounted the one above the other, and both facing in the same direction, so as to be
viewed at the same side of the case, substantially as specified.
2nd. A combined compass and clinometer in which the clinometer disc or card is
mounted above the compass card and faces in the same direction, and has a portion
or portions of it cut away to admit of the compass card being seen beneath it,
substantially as specified.
In witness whereof, I, the said Francis Barker, have hereunto set my hand
and seal this Third day of November. A.D. 1881.
Witness,
WM. CLARK,
53, Chancery Lane,
London,
Patent Agent.
FRANCIS BARKER. (L.S.)