IMPROVE- MENTS IN INSTRUMENTS FOR OBTAINING RIGHT ANGLES AND ASCERTAINING DISTANCES
Year: 1876

page_text: LETTERS PATENT to Henry Samuel Spiller Watkin, of Woolwich, in the
County of Kent, Captain, Royal Artillery, for the Invention of "IMPROVE-
MENTS IN INSTRUMENTS FOR OBTAINING RIGHT ANGLES AND ASCERTAINING
DISTANCES."
Sealed the 1st May 1877, and dated the 3rd November 1876.
PROVISIONAL SPECIFICATION left by the said Henry Samuel Spiller
Watkin at the Office of the Commissioners of Patents on the 3rd November
1876.
HENRY SAMUEL SPILLER WATKIN, of Woolwich, in the County of Kent, Captain,
Royal Artillery. "IMPROVEMENTS IN INSTRUMENTS FOR OBTAINING RIGHT ANGLES
AND ASCERTAINING DISTANCES."
This Invention relates to improvements in instruments for obtaining right angles
and ascertaining distances, and consists,―
1st. In the construction of a self-adjusting optical square, which contains within
itself the means of instantly testing and adjusting a true right angle.
2ndly. In the application of this principle to the common sextant, enabling
angles to be read up to 180° or more if required.
3rdly. In a range finder in which the above principle is applied together with
(A) a screw, angle, and range reader, by which angles or their corresponding
distances can be read for 15° on either side of the 0° without the aid of a Vernier,
and angles or their ranges from 15° on either side of the right angle; (B) a collar
sliding on a bar, which enables the range of any object being instantly given
without any calculation or mechanical calculation, and with any required base.
4thly. In a method of obtaining the length of a base by direct observations with
the instrument.
The Invention will be clearly understood by the following description and the
annexed Drawings.
1. The antical sunare. Figure 1. with the covering removed. A. B. C. D. is a square

page_text: or circular plate of metal or other material, having an index glass E of a sextant
screwed on to it. The horizon glass G is fixed on to a piece of metal F, H, capable
of pivoting round the centre G. At the end of the arm H, and at right angles to
it, is a steel screw, conical at both ends, with a square shoulder; on the bed plate
are soldered two metal blocks I and K, so arranged that the total possible traverse
of the arm F, H, with its screw, is an exact angle of 45°. It follows from this that
no matter what the position of the screw arm H, whether screwed in or out, the
total traverse of the arm will be the same. For as the end towards the block I is
withdrawn, the point towards the block K advances exactly the same amount, and
vice versa. Should then the arm H be pressed by a spring against the block I, and
the eye applied to the position L, the horizon glass may be adjusted by the screw H
with the aid of a key (fitting on to the square shoulder), that the image of a distant
object as seen by double reflection and by distant vision shall be coincident, in
the same manner as adjusting a sextant. Now if the arm H be pressed against the
block K, and the eye applied at the point M, objects O will be seen by double
reflection, and those at right angles to them by direct vision in the direction P.
Thus an optical square is produced, which admits of adjustment to an exact right
angle without the aid of any other instrument, should the mirrors be at any time
displaced or taken out. The method can be applied with equal facility to the index
glass, and also to non-reflecting instruments.
2. The application of this principle to the common sextant, enabling angles to
be read up to 180° or more if required. This will be easily understood from the
following consideration:-If in the ordinary sextant the limb be at 0°, the horizon
and index glasses will be parallel to one another, and thus the same object will be
seen by direct vision and by double reflection. If the former be now moved.
through an angle of 45° and the position of the eye also shifted, as already described,
for the optical square objects subtending 90° will be seen to coincide. Should this
limb be now moved along the graduated are objects subtending angles from 90° to
nearly 180° can be made to coincide, the reading on the arc, plus 90°, being the true
angle subtended.
3 and 4. The range finder, Fig. II., consists of a bed plate A, B, C, D, with an
arm E, F, pivoting at E, on which is fixed the index glass, the prolongation of
the side L, K, passing through the pivot E; M, the horizon glass screwed to an
arm M, N, and having a screw N¹, as described for the optical square, playing
between two blocks O, Q; V is a spring for the purpose of pressing the arm against
either block, notches being provided in the cover for this purpose. A bar R, S, is
fixed to the bed plate, having a collar sliding along it. An accurately constructed
screw of a suitable pitch, having a steel end turned to a conical point, works in a
block in this sliding piece. In prolongation of this screw and attached to it is a
boxwood cylinder U. From the sliding piece proceeds an index arm, the end of
which nearly touches the upper surface of the cylinder. A spiral spring T tends to
If now the screw
keep the arm E, F, pressed against the conical tip of the screw.
be withdrawn the arm E, F, and the mirror thereupon will be moved through an
angle, and the end of the index arm will describe a spiral on the cylinder. It will
only be necessary to mark this spiral in degrees and ininutes, or the ranges corre-
sponding thereto (in a right-angled triangle), in, say, a base of a hundred yards.
Now if the sliding piece be moved up or down the bar R, S, certain positions will
.be found, in which the same scale of angles or ranges will correspond to other
bases, say, from 50 to 130 yards, because the same movement of the screw will
produce a different movement of the arın E, F, depending upon the distance of the
point of the screw from the pivot E.
Another form, and in some respects a better one, is shown in Figure 3. Here,
instead of the bar R, S, being fixed it pivots on the point R, the block through
which the screw works is fixed to the bed plate, and the sliding collar has a steel
point fixed to press against the surfaces L, K. The remainder of this instrument
is the same as has been already described in Figure 2.

page_text: The method of working the range finder is as follows:-Two pickets A, B, are
planted about 100 yards from the observer C at a distance apart of 18 feet, the
sliding collar being pressed up to the pivot and the cylinder turned to 0° point. The
observer looks at the object the range of which is required, and moves backwards
or forwards until the picket B coincides with the object. As the arm M, M, has
been pressed against the block O the angle will be a right angle. The observer then
plants a picket and turns towards pickets A., B. The arm M, N, is now pressed against
the block Q, and the one picket reflected on to the other by revolving the cylinder;
the reading will be the exact distance. The collar is then moved along the
graduated bar to this distance. The observer now moves to the picket B, replacing
the arm in its original position, and looks at the object by direct vision; by moving
the cylinder the reflection of the picket C is made to be coincident with it. The
reading then will give the exact range. The whole time occupied in taking a range,
(including unpacking the instrument,) being 1 minutes.
For long ranges and obscure objects a telescope is provided, which can be inserted
at the eye holes to obtain exact coincidence, the approximate adjustment having
been obtained with the naked eye.
The advantages claimed for this instrument are,-
1. The ranges taken must always be correct, as any index error in the instrument
is at once detected.
2. The instrument is entirely self contained and capable of exact adjustinent
without the aid of other instruments.
3. No calculation or mechanical calculator is required, range being read direct.
4. The Instrument measures and works with any base.
5. No tripod or stand of any description is required.
6. Great portability is obtained, as the instrument is carried in a sling case over
the shoulder.
The same instrument can be adapted for infantry and naval use, and would
perhaps most conveniently take the form shown in Fig. 4. The mirrors and arms
are arranged as before, but for giving motion to the arm a cam may be conveniently
applied; the whole is included in a case, much the same in size and shape as an
ordinary box sextant. To the spindle of the cam is attached a pointer with an 0°
point and scale of yards.
The method of using this instrument is the same as those already described,
except that instead of turning the cylinder with its attached screw the cam is
moved by means of the index arm and the range is read off on the dial. The bar
projecting on the left of the instrument actuates the sliding collar, and adjusts for
different lengths of bases on the same principle as in the other instruments.
For naval purposes the bar would adjust for the height of the observer above the
sea level, the range scale being so graduated as to allow for the dip of the sea
horizon.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by the
said Henry Samuel Spiller Watkin in the Great Seal Patent Office on the 3rd
May 1877.
"
HENRY SAMUEL SPILLER WATKIN, of Woolwich, in the County of Kent, Captain,
Royal Artillery. IMPROVEMENTS IN INSTRUMENTS FOR OBTAINING RIGHT ANGLES
AND ASCERTAINING DISTANCES."
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by the
said Henry Samuel Spiller Watkin in the Great Seal Patent Office on the 3rd
May 1877.
HENRY SAMUEL Spiller Watkin, of Woolwich, in the County of Kent, Captain,
Royal Artillery. "IMPROVEMENTS IN INSTRUMENTS FOR OBTAINING RIGHT ANGLES
AND ASCERTAINING DISTANCES."
This Invention relates to improvements in instruments for obtaining right angles
and ascertaining distances, and consists.—
Firstly. In the construction of a self-adjusting optical square, which contains
within itself the means of instantly testing and adjusting a true right angle.
This Invention relates to improvements in instruments for
and ascertaining distances, and consists.-
obtaining right angies

page_text: Secondly. In the application of this principle to the common sextant, enabling
angles to be read up to 180° or more if required.
Thirdly. In a range finder in which the above principle is applied, together with
(A) a screw, angle, and range reader, by which angles or their corresponding
distances can be read for 15° on either side of the 0° without the aid of a Vernier;
and angles or their ranges from 15° on either side of the right angle; (B) a collar
sliding on a bar, which enables the range of any object being instantly given without
any calculation or mechanical calculator, and with any required base.
Fourthly. In a method of obtaining the length of a base by direct observations
with the instrument.
The Invention will be clearly understood by the following description and the
annexed Drawings:-
I. The optical square, Figure I., with the covering removed. A, B, C, D, is a
square or circular plate of metal or other material having an index glass E of a
sextant screwed on to it. The horizon glass G is fixed on to a piece of metal F, H,
capable of pivoting round the centre G. At the end of the arm H, and at right
angles to it, is a steel screw, conical at both ends, with a square shoulder; on the
bed plate are soldered two metal blocks T and K, so arranged that the total possible
traverse of the arm F, H, with its screw is an exact angle of 45°. It follows from this
that no matter what the position of the screw H, whether screwed in or out, the total
traverse of the arm will be the same, for as the end towards the block T is with-
drawn, the point towards the block Kadvances exactly the same amount, and vice versa.
Should then the arm H be pressed by a spring against the block T, and the eye
applied to the position L, the horizon glass may be so adjusted by the screw H with
the aid of a key (fitting on to the square shoulder) that the image of a distant
object as seen by double reflection and by direct vision shall be coincident in the
same manner as adjusting a sextant. Now if the arm H be pressed against the
block K and the eye applied at the point M, objects O will be seen by double
reflection, and those at right angles to them by direct vision in the direction P ; thus
an optical square is produced which admits of adjustment to an exact right angle
without the aid of any other instrument, should the mirrors be at any time dis-
placed or taken out. This method can be applied with equal facility to the index
glass, and also to non-reflecting instruments.
II. The application of this principle to the common sextant, enabling of angles to
be read up to 180° or more if required. This will be easily understood from the
following considerations:-If in the ordinary sextant the limb be at 0°, the horizon
and index glasses will be parallel to one another, and thus the same object will be
seen by direct vision and by double reflection. If the former be now moved
through an angle of 45°, and the position of the eye also shifted as already described
for the optical square, objects subtending 90° will be seen to coincide. Should the
limb be now moved along the graduated arc, objects subtending angles from 90° to
nearly 180° can be made to coincide, the reading on the arc, plus 90°, being the true
angle subtended.
III. and IV. The range finder, Figure II., consists of a bed plate A, B, C, D, with
an arm E, F, pivoting at E, on which is fixed the index glass, the prolongation of
the side L, K, passing through the pivot E; M, the horizon glass screwed to an
arm M, N, and having a screw N¹, as described for the optical square, playing
between two blocks O, Q; V is a spring for the purpose of pressing the arm against
either block, notches being provided in the cover for this purpose; a bar R, S, is
fixed to the bed plate, having a collar sliding along it; an accurately constructed 5
screw of a suitable pitch, having a steel end turned to a conical point, works in a
block on this sliding piece; in prolongation of this screw, and attached to it, is a
boxwood cylinder U; from the sliding piece proceeds an index arm, the end of
which nearly touches the upper surface of the cylinder; a spiral spring T tends to
keep the arm E, F, pressed against the conical tip of the screw. If now the screw
be withdrawn, the arm E, F, and the mirror thereupon will be moved through an

page_text: angle, and the end of the index arm will describe a spiral on the cylinder. It will
only be necessary to mark this spiral in degrees or minutes, or the ranges corre-
sponding thereto (in a right angle triangle), for, say, a base of a hundred yards.
Now if the sliding piece be moved up or down the bar R, S, certain positions will
be found in which the same scale of angles or ranges will correspond to other bases
say, from 50 to 130 yards, because the same movement of the screw will produce a
different movement of the arm E, F, depending upon the distance of the point of the
screw from the pivot E.
Another form, and in some respects a better one, is shown in Figure III. Here,
instead of the bar R, S, being fixed, it pivots on the point R, the block through
which the screw works is fixed to the bed plate, and the sliding collar has a steel
point fixed to press against the surface L, K. The remainder of this instrument is
the same as has been already described in Figure II.
a
The method of working the range finder is as follows:-Two pickets A, B, are
planted about 100 yards from the observer C at a distance apart of 18 feet, the
sliding collar being pressed up to the stop, and the cylinder turned to 0° point.
The observer looks at the object X, the range of which is required, and moves back-
wards or forwards until the picket B coincides with the object. As the arm M, N,
has been pressed against the block O, the angle X, C, B, will be right angle. The
observer then plants a picket, and turns towards pickets A, B. The arm M, N, is
now pressed against the block Q, and the one picket reflected on to the other by
revolving the cylinder. The reading will be the exact distance of B from C. The
collar is then moved along the graduated bar to this distance. The observer now
inoves to the picket B, replacing the arm in its original position, and looks at the
object by direct vision. By moving the cylinder the reflection of the picket C is
made to be coincident with it. The reading then will give the exact range, the
whole time occupied in taking a range (including unpacking the instrument) being
one and a half minutes.
For long ranges and obscure objects a telescope is provided, which can be inserted
at the eye holes to obtain exact coincidence, the approximate adjustment having
been obtained with the naked eye.
The advantages claimed for this Invention are,-
I. The ranges taken must always be correct, as any index error in the instrument
is at once detected.
II. The instrument is entirely self-contained, and capable of exact adjustment
without the aid of other instruments.
III. No calculation or mechanical calculator is required, the ranges being read
direct.
IV. The instrument measures and works with any base.
V. No tripod or stand of any description is required.
VI. Great portability is obtained, as the instrument is carried in a sling case over
the shoulder.
The same instrument can be adapted for infantry and naval use, and would
perhaps most conveniently take the form shown in Figure 4. The mirrors and
arms are arranged as before, but for giving motion to the arm a cam may be con-
veniently applied. The whole is enclosed in a case much the same in size and shape
as an ordinary box sextant. To the spindle of the cam is attached a pointer with a
0° point and scale of yards.
The method of using this instrument is the same as those already described,
except that instead of turning the cylinder with its attached screw the cam is
moved by means of the index arm, and the range is read off on the dial. The
bar projecting on the left of the instrument actuates the sliding collar and adjusts
for different lengths of bases on the screw principle, as in the other instruments; a
cam also has been applied for this purpose.
For naval purposes the bar would be adjusted for the height of the observer above

page_text: the sea level, the range scale being so graduated as to allow for the dip of the sea
horizon.
In witness whereof, I, the said Henry Samuel Spiller Watkin, have hereunto
set my hand and seal, this Twenty-eighth day of April, One thousand eight
hundred and seventy-seven.
HENRY SAMUEL SPILLER WATKIN. (L.S.)