Year: 1899

page_text: I, WALTER JOHN MURPHY, of 39, Courtfield Gardens, Earl's Court, London,
Cable Engineer and Electrician, do hereby declare the nature of this invention to
be as follows:-
This invention has for its object certain improvements in sextants designed to
overcome some of the disadvantages of these instruments as at present constructed
and with which it is necessary, after each sight at night time, that the instrument
be examined with a light to take the reading, thereby putting the eyes out of
accommodation and increasing the time required for the observation, which in
the case of a sight taken of the sun on a cloudy day is a great disadvantage.
Now in carrying this invention into effect I attach to the end of the screw of
the vernier a disc or wheel of any suitable metal or material upon the periphery
of which I form a series of indentations arranged at suitable intervals corre-
sponding to known movements of the scale operated thereby, and with which
indentations engages a suitable dog or tooth adjustable longitudinally upon an arm
or support attached to any convenient part of the instrument so as to
engage
any of the series of indentations aforesaid thereby enabling the person using the
instrument to make any adjustment by the sense of touch, the final reading being
taken with a light if at night.
with
I may instead of the device last described substitute therefor a worm wheel
engaging with the vernier screw and operated by means of a pawl and ratchet,
the movement of the pawl being adjustable so as to give a certain predetermined
movement to the said wheel.
I, WALTER JOHN MURPHY, of Duque de la Victoria, Vigo, Spain, late of 39,
Courtfield Gardens, Earl's Court, London, Cable Engineer and Electrician, 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:
This invention has for its object certain improvements in sextants designed to
overcome some of the disadvantages of these instruments as at present constructed

page_text: and with which it is necessary, after each sight at night time, that the instrument
be examined with a light to take the reading, thereby putting the eyes out of
accommodation and increasing the time required for the observation, which in
the case of a sight taken of the sun on a cloudy day is a great disadvantage.
In order that the invention may be the better understood drawings are appended.
Fig. 1 being a view of the back of a sextant to which the invention has been
applied.
Fig. 2 is a view of an alternative arrangement.
Figs. 3 and 4 are enlarged detailed views of certain parts of the instrument.
Referring to the drawings Fig. 1 it will be seen that instead of the milled head
usually attached to the end of the micrometer screw for adjusting the vernier
slide I provide the said screw with a disc or wheel c upon the periphery of
which I form a number of holes or recesses & so arranged that a spring tooth e
carried by the arm f shall engage with the said recesses thereby causing a slight
obstruction to the rotation of the wheel c and the amount of adjustment effected
by such portion of a revolution of the wheel being known the adjustment may be
effected by the sense of touch. I may instead of providing the disc or wheel with
one set of recesses, form a series as shown in Fig. 3 around the periphery thereof,
the spacing or pitch of each series being different so that a means of adjustment
being provided for the spring tooth e, it may be caused to engage with any series
of holes and by this means the amount of adjustment may be varied as desired.
Instead of forming the holes or recesses as aforesaid upon the periphery of the
wheel or disc c I may form them upon the side of the said disc and provide a spring
tooth-g supported within the hollow arm-h-which-tooth-will-engage with the recesses-
in the side of the wheel and act in a similar manner as in the preceding cases.
A spring i may be provided and may be attached at one end to a pin jupon.the
plate k secured to the vernier slide nut and at the other to a pin 7 thus pulling
against the-screw-a-and-preventing-any-back-lash-due-to-wear-of the-same,-or, the
nut through which the screw passes.
1.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I-claim is:
1. In a sextant the provision of a means whereby a known adjustment of the
vernier may be readily effected at night time without the aid of a light.
2. The improvements in sextants substantially as herein described and illus-
trated by the appended drawings.
"
Dated this 14th day of Va
1
1000
"