IMPROVEMENTS IN APPARATUS FOR MEASURING DISTANCES BY ANGLES OF DEPRESSION IRRESPECTIVE OF HEIGHT, AND DETERMINING THE DISTANCES THEREBY
Year: 1870

page_text: LETTERS PATENT to John William Spiller Watkin, M.A., of Ship-
.
bourne Vicarage, near Tunbridge, in the County of Kent, for the
Invention of "IMPROVEMENTS IN APPARATUS FOR MEASURING DISTANCES BY
ANGLES OF DEPRESSION IRRESPECTIVE OF HEIGHT, AND DETERMINING THE
DISTANCES THEREBY." - A communication from abroad by Henry
Spiller Watkin, of Gibraltar, Lieutenant in Her Majesty's Royal
Artillery.
"
-
Sealed the 9th December 1870, and dated the 2nd July 1870.
PROVISIONAL SPECIFICATION left by the said John William Spiller
Watkin, M.A., at the Office of the Commissioners of Patents, with
his Petition, on the 2nd July 1870.
I, JOHN WILLiam Spiller Watkin, M.A., of Shipbourne Vicarage,
near Tunbridge, in the County of Kent, do hereby declare the nature of
the said Invention for "IMPROVEMENTS IN APPARATUS FOR MEASURING DIS-
TANCES BY ANGLES OF DEPRESSION IRRESPECTIVE OF HEIGHT, AND DETERMINING THE
DISTANCES THEREBY," to be as follows:-
The object of this Invention is to construct an apparatus of a portable
nature so that it can be moved about with facility for measuring angles

page_text: of depression of whatever kind, irrespective of height, and determining
the distances thereby to any extent within range of the eye or the
telescope with the greatest accuracy.
The apparatus is constructed as follows:-I take a case or box of any
suitable shape, and I connect the two ends of a bent glass tube at or
near its upper & lower part; the tube is arranged at an angle or
horizontally. The box is to be partly filled with liquid, and the top
hermetically closed against access of air or escape of liquid. I propose
to mark one or both of the legs of the tube with a scale or indicator,
which represent degrees, minutes, and divisions of minutes, or to place a
scale so divided in close proximity to it or them; the box and tube is
then fitted in a frame or case to preserve them from injury. The box
forms the reservoir for the liquid, and rests upon the outer frame or case
by pins or otherwise, while the tube end of the frame is free to be raised
and lowered within certain limits, and also retained at any intermediate
point by a thumbscrew, which rides in a slotted bar pinned to the frame.
The top surface of the frame is perfectly straight, and for moderate
distances, such as those visible to the naked eye, the line of sight could
be taken along it, of course raising the free end of the apparatus to
bring it in line therewith at the same time; but where long distances
have to be brought within view a telescope can be arranged on the top,
and the frame raised or lowered accordingly. As the apparatus is tilted
or inclined to bring it in a line with the distant object the liquid rises
or falls in the leg, and the scale indicates it accordingly.
Other scales, rules, or appliances can also be fitted to the sides of the
frame if found convenient.
To enable the measurements to be taken in all directions I arrange
the frame on the central pivot of a stand, and in such a case the
apparatus will be found of great service to the surveyor and leveller, as
it would answer all the purposes of a dumpy or other level.
The apparatus is applicable for civil engineering and for military
purposes generally.
It is not essential to use a stand in connection with this apparatus.
In many cases it may be desirable that the box or reservoir should not
be a separate adjunct of the instrument, but in continuous connection.
with the legs of the tube.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said John William Spiller Watkin, M.A., in the Great
Seal Patent Office on the 2nd January 1871.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
WILLIAM SPILLER WATKIN, M.A., of Shipbourne Vicarage, near.
Tunbridge, in the County of Kent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her.
Letters Patent, bearing date the Second day of July, in the year of our
Lord One thousand eight hundred and seventy, in the thirty-fourth year
of Her reign, did, for Herself, Her heirs and successors, give and grant
unto me, the said John William Spiller Watkin, Her special licence that
I, the said John William Spiller Watkin, my executors, administrators,
and assigns, or such others as I, the said John William Spiller Watkin,
my executors, administrators, and assigns, should at any time agree with,.
and no others, from time to time and at all times thereafter during the
term therein expressed, should and lawfully might make, use, exercise,
and vend, within the United Kingdom of Great Britain and Ireland, the
Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
APPARATUS FOR MEASURING DISTANCES BY ANGLES OF DEPRESSION IRRESPECTIVE OF
HEIGHT, AND DETERMINING THE DISTANCES THEREBY," (communicated to me
from abroad by Henry Spiller Watkin, of Gibraltar, Lieutenant in Her
Majesty's Royal Artillery, upon the condition (amongst others) that I,
the said John William Spiller Watkin, my executors or administrators,.
by an instrument in writing under my, or their, or one of their hands.
and seals, should particularly describe and ascertain the nature of the
said Invention, and in what manner the same was to be performed,
and cause the same to be filed in the Great Seal Patent Office within
six calendar months next and immediately after the date of the said.
Letters Patent.
NOW KNOW YE, that I, the said John William Spiller Watkin, do
hereby declare the nature of the said Invention, and in what manner
the same is to be performed, to be particularly described and ascertained
in and by the following statement thereof, reference being had to the
Drawings hereunto annexed, that is to say :-
The object of this Invention is to construct an apparatus of a portable
nature so that it can be moved about with facility for measuring angles

page_text: of depression of whatever kind, irrespective of height, and determining
the distances thereby to any extent within range of the eye or the
telescope with the greatest accuracy.
The instrument is to be called the hydro-clinometer with calculating
scale, and is constructed as follows:-The Inventor forms a reservoir of
any suitable shape and material, with an opening in its upper side, or top,
or elsewhere, and with this reservoir, at or near its upper and lower part,
are connected the two ends of a bent glass tube. The tube is arranged
at an angle or horizontally. The reservoir is partly filled with fluid, and
the opening hermetically closed so as to prevent any escape of the
liquid employed. One or both of the legs of the tube is or are marked
with a scale or indicator representing degrees, minutes, and divisions of
minutes, and when needed another scale is placed in close proximity to
the legs of the tube, and so constructed as for given heights to represent
at once the distances corresponding to the angles of depression or
clevation indicated by the position at which the fluid subsides. The
reservoir and tube are fitted in a frame or case to preserve them from
injury. Over the reservoir a shield of wood or other material is fixed by
screws or otherwise, and when necessary some non-conducting substance
is inscrted between the shield and reservoir to prevent any effects from
changes of temperature upon the fluid and reservoir. The top surface of
the frame of the instrument will, as a rule, be made perfectly straight,
and when so made, for moderate distances, such as those visible to the
naked eye, the line of sight could be taken along it; but where long
distances have to be brought within view and great accuracy is required
a telescope is placed on the upper edge of the instrument and adjusted at
an angle or otherwise to the horizon. The instrument, whether to bo
used with or without a telescope, is accurately graduated by a theodolite.
The under surface of the frame of instrument may be perfectly horizontal,
or otherwise, but when the instrument is to be used as a level this
surface must be horizontal, or projections by screws or in some other
way may be attached to secure horizontality.
When the instrument is used as a distance measurer it is made to
rest on its reservoir end; it is next elevated or depressed by laying
hold of the other end, and to the extent necessary to bring its upper
edge or the telescope in line with the distant object; the liquid
descends or ascends the glass tube, and its position when at rest
indicates the angle required by the observer through the scale attached.

page_text: The instrument is firmly held in any position by a thumbscrew riding in
a slotted bar, shown in Figure 3, pinned to the case of the instrument,
and capable of rotating into a perpendicular position or otherwise.
Other scales, rules, or appliances can be fitted to the frame. For
example, to enable the measurements to be taken very rapidly in all
directions the frame is arranged or the case so as to be fixed on the
central pivot of a stand, where a horizontal or vertical motion may be
given to the instrument. So adapted the instrument when fitted up as
a level will be found of great service to the surveyor and leveller by
answering the purposes of a dumpy or other level.
The instrument with or without a stand is applicable for civil
engineering and for military purposes generally.
The Invention will be well understood by referring to the accom-
panying Drawings, of which Figure 1 is a view of the outer casing or
support for the reservoir and tube, the reservoir occupying the hollow or
cut-away portion a, and the tube in connection with reservoir the
spaces b, c. The tube is held in its place by a groove in the frame and
by cement, and over the reservoir is a shield screwed to frame, as shown
in Figure 3 by letter g. Round and within the legs of the tube a piece
of white wood is placed to carry the scales, but in some cases for greater
protection the white wood covers the top leg of tube, and is of the
shape shown in Figure 2, extending when fixed to frame, as in Figure 3,.
from inner end of reservoir to f. In this case the leg 6 of the tube is
enclosed and the lower leg c exposed to view, above which the scale is
placed. The angle of depression is read off from the tube with great
facility, as the upper point of the liquid coincides with the figure or
mark indicating the angle, and to give greater facility to the reading the
fluid may be coloured with any suitable colour.
One end of the instrument, as represented in Figures 1 and 3, may bo
deeper than the other, but it is only so made when the instrument is
intended only to be a distance measurer in order to render it more light.
In Figure 3 the instrument is shown as tilted at its fore end for use.
The upper point of the fluid rests under the figure 2 on the scale, and
the object sighted indicates therefore an angle of depression amounting
to two degrees, and supposing the telescope reversed and the observer
looking up to an object, and the fluid resting at the same point, the
angle of elevation indicated would be of the same amount. One of the

page_text: chief advantages in the instrument is that very small angles to the
extent of a half minute can be read off by the naked eye. On the
surface of the shield of reservoir indicated by letter g is engraved the
following formula, available for calculating the distances of objects for
small angles of depression or elevation when the height is known :—
100 x 1146
100'
Height in feet of battery x 1146
Angle of depression in minutes =range in yards.
For small angles this simple formula enables the observer to find very
quickly the distance of the object sighted. Suppose the height in
feet to be 100, suppose the angle of depression to be 100', then
1146 yards for distance of object. The necessity however of
finding the distance by the above formula is obviated by the use of the
calculating scale, which may be defined a ready reckoner. This scale
is represented in Figure 4, and is a skilful adaptation of the formula
within certain limits. The scale has three divisions. Upon the upper
division are arranged heights from 50 to 400 feet; on the middle angles
from 30' to 9° or 10° upon a slide j, with arrow ↓ at end %; on the
third ranges or distances in yards from 500 to 6000. This scale might
commence lower and be extended higher, but it is specially adapted for
range firing. Suppose a person with this scale in his hand standing
on an eminence of 50 feet, and sighting an object having an angle of
depression of fifty minutes. On the middle division he observes 50'; he
slides the 50' until it coincides with the height 50 feet, the arrow on the
slide then points to the range or distance, namely 1146 yards.
The calculating scale may be affixed to back of instrument, or
may be had detached from the instrument, and is applicable to any
distance measurer by means of angles of depression or elevation. The
instrument with the scales is fitted up in a strong box, and all may be
so constructed as to be of small and very portable dimensions. A small
portable instrument of this kind with a good pocket barometer graduated
for heights would be a very amusing companion to a tourist fond of
measuring heights and distances. Suppose no great atmospheric changes
taking place, and an actual elevation of 150 feet attained, and an
object sighted at an angle of depression of 30', the distance by the scale
or the formula would be 5730 yards
The formula upon the
instrument is easily found by persons slightly acquainted with
trigonometry and furnished with mathematical tables.
=
150 x 1146
30

page_text: HANTAI
z should not be taken at any angle less than 90, and must be taken at
such an angle beyond 90 as will secure the fall of rays of light from any 1
object O upon the intersection of axis A, C, at E. If z be taken at 95°
then x=10++d, and when the axis is horizontal d=0 and -10. When
the axis is depressed below the horizontal line d becomes negative, and
when d=10, z=0. By moving the instrument up and down and
catching the objects required, angles of elevation would thus be found 2
from 0 to 10+d, and the limit of such angles would therefore depend
upon the extent of graduation of d. This is another application of the
instrument contemplated by the Inventor.
The hydro-clinometer is regarded by the Inventor as an instrument
which must result in great saving to the public funds, if applied for war
purposes, as it will prevent the necessity of many expensive trial shots
for ascertaining ranges; and any gunner may by its use know almost
immediately the distance of any object within reach of the gun.
And having now described the nature of the said Invention, and in
what manner the same is to be performed, I declare that I claim,—
Firstly. The construction and employment of apparatus for measuring
distances by angles of depression irrespective of height, so that the
distances can be determined thereby, substantially in the manner
herein-before described and shown.
Secondly. I claim forming and arranging scales on or to a frame in
which a bent glass tube is fitted, so that distances can be determined

page_text: by angles of depression or of elevation in the manner shown and
described.
Thirdly. I claim the employment of such instruments with or without
a stand or support, so that they can be used for levelling and other
similar purposes, substantially as described.
In witness whercof, I, the said John William Spiller Watkin, have
hereunto set my hand and seal, this 28th day of December,
in the year of our Lord One thousand eight hundred and
seventy