Improvements in Sextants with Artificial Horizon.
Year: 1893

page_text: Date of Application, 5th Jan., 1893-Accepted, 18th Feb., 1893
COMPLETE SPECIFICATION.
Improvements in Sextants with Artificial Horizon.
I, SAMUEL HUBBARD JAMES of 3 Douglas Villas, Streatham Common London
Civil 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 :-
Whereas numerous attempts have been made to obtain a practical artificial
horizon for use at sea, the attempts have all been directed to some contrivance to
obtain a steady horizontal surface in a rolling ship, as yet an impossibility. The
object of this invention is to be able to take an altitude with a wobbling artificial
horizon.
By reference to the drawings it will be seen that I make no attempt to keep my
artificial horizon glass A perfectly horizontal but allow it to swing freely, but at
the same time I also make the ordinary horizon glass B swing with it both being
fixed in the same swinging frame, swinging on the pivots C, both must swing exactly
alike and compensate each other's errors.
I have purposely omitted shewing adjustments well known to every instrument
maker, and have only shewn the two specially desirable for this invention.
Fig. 1 is an end view of the swinging frame attached to a sextant, said swinging
frame containing both horizon glass B & also artificial horizon glass A both these
glasses being permanently fixed in the swinging frame by suitable adjustments.
Fig. 2 is a sextant with the said swinging frame shewn in section attached this
shews approximately the positions of the horizon glass B and artificial horizon
glass A in said swinging frame which swings upon the pivots at C quite inde-
pendently of the object glass O. In order to approximately adjust the centre of
gravity of this swinging frame I provide a weight W which by means of a screw
passing through it, can be shifted backwards or forwards as desired.
glasses A & B swing absolutely together there is no necessity for the artificial
horizon glass A to be horizontal for the apparent error due to this cause is com-
pensated by precisely a similar error due to the same movement of the horizon
glass B.
As both
I am well aware that there is nothing new in a swinging artificial horizon glass
of itself attached to a sextant & I am equally well aware that such devices are
useless & I make no claim therefor, but as will he seen hereafter I do claim horizon
glass & artificial horizon glass both fixed in the same swinging frame swinging
independently of the object glass O-that being the essence of the invention.
With ordinary sextants graduated only up to 140 degrees it would only be
possible to take altitudes with an artificial horizon up to one half or 70 degrees and
as the same instrument would be wanted to take higher altitudes in the tropics-
lunar distances & horizontal angles I provide a screw adjusting clamp S which by
clamping the swinging frame, will enable the instrument to be used as an ordinary
fixed sextant.
I use suitable adjustments for adjusting to zero & so forth but do not limit myself
to minor adjustments shewn or not shewn but use any or all of the well known
means for these purposes, & telescopes, eye pieces dark glasses &c. which are not
shewn.
Having now particularly described & ascertained the nature of my said inven-
tion & in what manner the same is to be performed, I declare that what I
claim is
1. The combination of a sextant and swinging frame said frame containing both
1
1 havinan class full.

page_text: silvered) fixed therein said swinging frame swinging bodily independently of the
object glass substantially as described.
2. A sliding weight which can be adjusted to alter the centre of gravity of said
swinging frame. substantially as described.
.
3. A clamp to convert said swinging frame into a fixed one, in order to use the
instrument as an ordinary sextant—substantially as described & for the purpose set
forth.
S. H. JAMES.