AN IMPROVED LEVELLING AND SURVEYING INSTRUMENT
Year: 1878

page_text: LETTERS PATENT to John Townsend Trench, of Kenmare, in the County of
Kerry, Ireland, and George Charles Ferdinand Barnardo, of 10, Lower Fitz-
william Street, Dublin, Ireland, for the Invention of "AN IMPROVED
LEVELLING AND SURVEYING INSTRUMENT."
Sealed the 14th May 1878, and dated the 18th March 1878.
PROVISIONAL SPECIFICATION left by the said John Townsend Trench and
George Charles Ferdinand Barnardo at the Office of the Commissioners of
Patents on the 18th March 1878.
-
JOHN TOWNSEND TRENCH, of Kenmare, in the County of Kerry, Ireland, and
GEORGE CHARLES FERDINAND BARNARDO, of 10, Lower Fitzwilliam Street,
Dublin, Ireland. "AN IMPROVED LEVELLING AND SURVEYING INSTRUMENT.”
The object of this Invention is the production of a simple and portable instrument,
serving both for levelling and for measuring horizontal angles.
The apparatus consists of a small telescope and a large spirit level fixed side by
side upon a plate. The spirit level has two screw legs which pass through the plate
and receive nuts both on the upper and under side of it. By means of the nuts the
spirit level can be adjusted, so that the bubble stands in the middle when the axis
of the telescope is horizontal. The plate itself is fixed on the upper end of a stém
or axis, which is received into a cylindrical socket. This socket is carried by a
tripod stand in the following manner-Upon the tripod a dome or inverted cup is
screwed, and in the top of the dome there is an opening to receive the lower end of
the socket which has a thread upon it. A semi-globular nut is screwed on to the
socket beneath the dome or inverted cup, so forming a joint connecting the socket
with the tripod and admitting of the movement requisite for setting the telescope
level. This is accomplished as in other instruments of the class by means of four
levelling screws. The socket has a flange upon it with holes tapped to receive the
levelling screws, and there is another similar but unperforated flange upon the
exterior of the dome.
'

page_text: In setting the instrument the levelling screws are turned until their lower ends
all bear upon the lower flange.
The circle for reading angles is graduated to degrees, and is fixed upon a collar
which surrounds the socket immediately above its flange; the collar and graduated
circle can turn freely on the socket, but it may also be locked at pleasure by a
binding screw. The binding screw is carried by an arm fixed to the flange of the
socket. Immediately above the angle circle there is a disc of the same diameter
fixed to the plate which carries the telescope and spirit level, and on the edge of
this disc a vernier is engraved, by which the angle circle can be read to minutes.
In setting up the instrument for use it is adjusted by the levelling screws as
already described. The levelling is carried on in the usual manner, and
simultaneously whenever desired horizontal angles may be measured. To measure
the horizontal angle between two objects the telescope to which is attached the
vertical axis and upper plate and vernier is laid first on one object, and then the
moveable graduated circle is set to zero, and clamped; then the telescope is moved
round to the other object, and the required angle is read off at once from the circle
being thus obtained without any calculation or subtraction. This is an important
point in the use of the instrument, as it avoids writing down unnecessary figures
and lessens the risk of error.
The instrument is especially intended for making rapid preliminary surveys.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Townsend Trench and George Charles Ferdinand Barnardo in
the Great Seal Patent Office on the 18th September 1878.
JOHN TOWNSEND TRENCH, of Kenmare, in the County of Kerry, Ireland, and
GEORGE CHARLES FERDINAND BARNARDO, of 10, Lower Fitzwilliam Street,
Dublin, Ireland. "AN IMPROVED LEVELLING AND SURVEYING INSTRUMENT."
The object of this Invention is the production of a simple and portable instru-
ment, serving both for levelling and for measuring horizontal angles.
The Drawing hereunto annexed shews an instrument construment according to
our Invention.
Figure 1 is a side elevation; Figure 2, a side elevation partly in section; and
Figure 3, a plan view.
It consists of a small telescope marked A, and large spirit level B held side by
side upon a plate C, and both being held parallel with the plate; this plate is fixed
by small screws D on the upper end of a stem or axis E which is received in a
cylindrical socket F. The socket is carried by a tripod stand in the following
manner: Upon the top of the tripod is screwed a dome or inverted cup G; in the top
of the dome is an opening to receive the lower end of the socket F; H is a semi-
globular nut screwed on to the socket beneath the dome. The joint formed con-
nects the socket with the tripod, and yet allows sufficient movement to admit of

page_text: the plate carrying the telescope being set horizontally. This is accomplished as in
other instruments of the class by means of four levelling screws. The socket has
upon it a flange F1 with holes tapped in it to receive the levelling screws F*; there
is another similar but unperforated flange G' on the exterior of the dome G.
In setting the instrument the levelling screws are turned until the plate C is
brought to a horizontal position, and the lower ends of the screws all bear upon the
lower flange.
The circle I for reading angles is graduated to degrees, and is fixed upon a collar
I which surrounds the socket F immediately above its flange F¹. The graduated
circle turns freely around the socket, but can also be locked to it at pleasure by a
clip J, shewn clearly at Figure 4.
In the instrument shewn in the Drawings the clip is composed of two plates
which can be drawn together by a screw J', and caused to grip a flange on the
under side of the circle I.
The lower plate of the clip has connected to it a boss J, through which passes a
tangent screw J, and this screw screws into a lump J' on the flange F¹ which sur-
rounds the socket before mentioned. Thus the clip can not only be used for locking
and holding the circle I, but by turning the tangent screw J³ when the clip is
holding this circle the circle can be set at zero with great accuracy. Immediately
above the angle circle I there is a disc K of nearly the same diameter fixed by the
small screws D to the under side of the plate C which carries the telescope and
spirit level. On the edge of this disc a vernier is engraved, by which the angle
circle I can be read to minutes; or if the circle I and disc are made of larger
diameter the angles might of course be read to a greater degree of nicety.
When the instrument has been set up and adjusted as above-described so as to
bring the plate C into a horizontal position, levelling can be carried on in the
ordinary manner, or horizontal angles may be measured. To measure the horizontal
angle between two objects the plate C together with the telescope A and
with the disc K on the edge of which the vernier is engraved is turned until
the telescope is laid on one object. The graduated circle I is then roughly
set to zero and clamped by the clip J; it is then brought accurately to zero by
turning the tangent screw Js in whichever direction is required. The telescope
with the plate C and disc K are then turned until the telescope is laid on the other
object. The required angle can then be read off at once by the vernier marked on.
the disc K upon the circle I, without any calculation or subtraction. This is an
important advantage obtained by the use of instruments constructed as above
described, as the writing down of unnecessary figures is avoided and the risks of
error are lessened.
In order to render the instrument available for taking horizontal angles not only
between objects which are approximately on the same horizontal plane in which
the telescope pivots, but also between objects which may be either above or below
this plane, we place on to the forward end of the telescope a tube L carrying two
mirrors M and N. One mirror M is mounted on a horizontal axis M², at the edge
of the tube L; the other mirror N is mounted on another horizontal axis N¹, which is
in a vertical line above the centre of the mirror M. The mirror M can be held by
spring clips M2 at an angle of 45° to the axis of the telescope; the mirror N can be
inclined to any desired angle by the lever handle N2, which is at one end of the
axis N'. When the telescope is to be directed on an object in the same plane as
the telescope, the mirror M is released from the spring clips which hold it up, and is
allowed to hang down, as shown by dotted lines, clear of the front of the telescope;
the objects are then seen direct through the telescope. If one of the objects between
which the horizontal angle is to be measured is above the plane of the telescope the
mirror M is turned up into the piston shewn in the Drawing, and the mirror N is
inclined until the object is reflected into the telescope. If the object to be observed
is below the plane of the telescope a half turn is given to the tube L which carries
the mirrors, and then an object below the plane of the telescope can similarly be
brought into view.

page_text: In order to ensure that whenever the tube L is turned round from one position
to another that the axis of the mirrors shall always be brought into a horizontal
plane, the edge of the tube which is towards the telescope has two small nicks
accurately cut in it at opposite points of its circumference, and when the tube is in
one or other of its correct positions one or other of these nicks fit on to a small pin
or projection in the telescope. When a half turn is to be given to the tube the tube
is drawn forward to free the nick in it from the pin; the tube can then be turned
freely, and when a half turn has been given to it the tube is pushed back to cause
the other nick in it to embrace the pin.
In order that the spirit level may be set accurately parallel with the plate C it is
carried near its extremities by two screw pins which pass through the plate, and on
to each of which are screwed two nuts, one above and the other below the plate; by
turning these screws the position of the level can be varied, and when adjusted can
be held by all the nuts bearing against the plate.
In order that the instrument may be adapted for setting out straight lines, and
in order to facilitate the adjustment of the telescope so that its axis shall be parallel
with the plane of the plate C, the telescope may be laid into V slots in two
standards 0, 0, as shown in the Drawing; one of these standards is carried by a
screw stem which passes through the plate C, and has nuts screwed on to it, one above
the other below the plate, so that the standard can be raised or lowered as neces-
sary and locked in the required position. The telescope can also be turned in the V
slots, and the diaphragm carrying its cross wires be accurately adjusted by screws
P in the ordinary manner; the telescope can thus be reversed end for ond in its
standards and used in the well-known manner for setting out straight lines. When
thus used the circle I and disc K can be locked together to prevent any chance of
their shifting in position by means of a clamp worked by a screw R, as shown at
Figure 5. The telescope is held down into the V slots by straps S, which may also serve
to lock the telescope in the manner shewn, and prevent its turning in order that the
axis of the mirrors shall always be retained in a horizontal plane, or other provision
may be made for effecting this object.
.
If it is not required that the telescope should be capable of reversal it may be
permanently secured to the plate C, parallel to the plane of this plate, and this for
many purposes, especially for the use of architects for laying out large buildings
accurately would be the preferable form in which to construct the instrument, as it
would be cheaper, and the various other adjustments would not be necessary.
The instrument might also be made without the tangent screw used for setting
the circle with extreme accuracy to zero.
By mounting the telescope and spirit level side by side on one base plate, as
above described, and one on either side of the pivot on which the plate is free to
turn, a spirit level of comparatively large dimensions can readily be used, so that
although the instrument is of small size as compared with other levelling instru-
ments, yet it can be set as truly and accurately as the larger instruments, and at the
same time the plate on which the spirit level and telescope are mounted being short
and broad, great steadiness is obtained with little liability of injury.
Also by having the upper horizontal ring on which the vernier is marked in close
proximity to the plate upon which the level and telescope are mounted great
steadiness is obtained.
The instrument is also cheap in construction and very portable, being of light
weight and readily packed.
Having thus described the nature of our said Invention, and the manner of
performing the same, we would have it understood that we claim,—
First. The improved levelling and surveying instrument, substantially as described
and illustrated in the annexed Drawings.
Second. The combination of the telescope A, spirit level B, stem or axis E, socket
F, which, by levelling screws, can be set upright upon a tripod or suitable stand,
vernier K, and angle circle I, so arranged that the vernier can be set to zero in any
position of the telescope, all substantially as herein described.
•

page_text: Third. The combination of the telescope A, mounted side by side with a
spirit level B on the plate C, free to turn on a stem or axis E, as herein-before
described.
Fourth. The combined arrangement, substantially as herein-before described, for
enabling objects either above or below the axis of the telescope of levelling
instruments being brought into the field of view of the telescope.
In witness whereof, I, the said George Charles Ferdinand Barnardo, have
hereunto set my hand and seal, this Sixteenth day of September, in the year
of our Lord One thousand eight hundred and seventy-eight.
GEORGE CHARLES FERDINAND BARNARDO. (L.S.)