A NEW SURVEYING INSTRUMENT
Year: 1866

page_text: LETTERS PATENT to David Reid Edgeworth, of 13, Queen Square, in
the City of Westminster, Civil Engineer, for the Invention of "A NEW
SURVEYING INSTRUMENT."
Sealed the 24th October 1866, and dated the 28th April 1866.
PROVISIONAL SPECIFICATION left by the said David Reid Edgeworth
at the Office of the Commissioners of Patents, with his Petition, on the
28th April 1866.
I, DAVID REID EDGEWORTH, of 13, Queen Square, in the City of Westminster,
Civil Engineer, do hereby declare the nature of the said Invention for "A
NEW SURVEYING INSTRUMENT," to be as follows:-
The object of this Invention is to enable the surveyor to draw the plan of
the portion of country or land to be surveyed while the survey is proceeding,
whereby the ordinary survey book and the necessity of afterwards drawing the
plan are dispensed with.
My new instrument is constructed as follows:-I fit above an ordinary-
tripod stand a table or platform, to which a sheet of paper or other suitable.
material is secured. This table is capable of being placed on a level with the
plane of the horizon, and of being adjusted to correspond with the line of the
ground along which it is required to survey. Above and around this table is a
frame free to move independently of the table, and carrying a telescope; it also

page_text: carries a scale, which is close to the surface of the paper on the table, and
which moves with the telescope. The telescope has a vertical motion in its
bearings produced by an excentric or otherwise, by which on observing an
ordinary levelling staff at a distant point the distance of this point can be
accurately determined, and immediately plotted on the paper by means of the
scale below, which is in a line with its direction. The telescope has also a
vertical motion in the plane of the meridian to enable it to be set or brought
to any low or high points of the surrounding country, and a scale is attached
to it to convert bypotheneusal into horizontal measurements.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said David Reid Edgeworth in the Great Seal Patent Office on
the 27th October 1866.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, DAVID
REID EDGEWORTH, of 18, Queen Square, in the City of Westminster, Civil
Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date.the Twenty-eighth day of April, in the year of our Lord
One thousand eight hundred and sixty-six, in the twenty-ninth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said David Reid Edgeworth, Her special licence that I, the said David
Reid Edgeworth, my executors, administrators, and assigns, or such others
as I, the said David Reid Edgeworth, 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 "A NEW SURVEYING INSTRUMENT," upon the condition (amongst
others) that I, the said David Reid Edgeworth, 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 David Reid Edgeworth, do hereby
declare the nature of my said Invention, and in what manner the same is
to be performed, to be particularly described and ascertained in and by the

page_text: following statement thereof, reference being had to the Drawings hereunto
annexed, that is to say :-
The object of this Invention is to enable the surveyor to draw the plan of
the portion of country or land to be surveyed while the survey is proceeding,
whereby the ordinary survey book and the necessity of afterwards drawing the
plan are dispensed with.
My new instrument is constructed as follows-I fit above an ordinary
tripod stand a table or platform, to which a sheet of paper or other suitable
material is secured. This table is capable of being placed ou a level with the
plane of the horizon, and of being adjusted to correspond with the line of the
ground along which it is required to survey. Above and around this table is
a frame free to move independently of the table, and carrying a telescope; it
also carries a scale, which is close to the surface of the paper on the table, and
which moves with the telescope: The telescope has a vertical motion in the
plane of the meridian to enable it to be set or brought to any low or high
points of the surrounding country, and a scale is attached to it to convert
bypotheneusal into horizontal measurements.
Figures 1 and 2 of the accompanying Drawings are elevations of the two
sides of one of my surveying instruments:
A is a table or platform, shown detached in plan in Figure 3. It is marked
off with degrees as shown, and is provided with clips or holders a, a, for
securing a sheet of paper or other suitable material thereon. It is supported
by a pillar B; the lower end of which carries a collar C, screwed or otherwise
firmly secured to an ordinary tripod stand (not shewn). The table A is; as
before stated capable of being placed on a level with the plane of the horizon;
and of being adjusted to correspond with the line of the ground along
which it is required to survey.
The adjustment is effected by means of screws Dresting at their lower end
on a plate E formed in a piece with the collar C; and working in nuts in a
plate F fixed to the pillar B. The lower end of this pillar is fitted into the
collar C in such manner that the pillar is free to be raised or lowered at any
part required by the screws D. Above and around the table A is a frame G;
free to move in a circular direction independently of the table, and fixed in
any required position by a clamping screw H passed through a, collar I of
the frame G; so as to bear against the pillär B. The frame G carries &
telescope J fitted with an ordinary spirit level K, and with a diaphragm having
two horizontal hairs distant from one another; say, a hundredth part of the
actual distance from the eye (when' applied to the instrument) to the hairs
measured along the optical axis; the-frame also carries a scale L close to th

page_text: surface of the paper on the table A; the centre of this scale corresponds with
the centre of the instrument, and it is graduated to the scale to which the
surveyor wishes to have his survey plotted, this scale L has a portion removed
near each end at b to allow it to pass over the clips a when turning. The
telescope J has a vertical motion in the plane of the meridian on the pivot M
to enable it to be set or brought to any low or high points of the surrounding
country, this motion may be produced by a tangent screw N or otherwise, and
the telescope is fixed in the required position in the plane of the meridian by
means of a clamping screw O. P is a scale attached to the telescope to
convert hypotheneusal into horizontal measurements; Q is a nonius. From
the distance of the hairs of the telescope it follows that when an ordinary
levelling staff is held on any distant point and the telescope brought to bear
upon it, if the readings in feet and decimals of the intersections of the wires
on the staff be observed, that difference being, multiplied by a hundred gives
the true distance in feet of the staff from the instrument. There is thus a
simple and speedy method provided of measuring the distances around the
instrument. However, some correction of this method must be made in
obtaining distances in precipitous grounds, in such cases it is necessary that the
staff should be held at right angles to the axis of the instrument observing it,
and not upright as the staff man would feel naturally disposed to hold it. Thus
the operation of determining a distance in precipitous ground is as follows:-
The instrument is at the point A, (see Figure 4), and the horizontal distance
A, F, is what is required to be known. The man holding the staff should
sight the instrument through a hole bored square through the staff at C or by
any other convenient device, and when he sights the instrument the staff must
necessarily be square to the line of sight. He then signals to the observer,
who takes the readings at E and D, the difference of which multiplied by 100
is the true distance from C to A. This corrected by the hypotheneusal
excess gives the horizontal distance A, F. It is to be observed that these
corrections are not necessary except in precipitous places; and that as a general
rule, when the obliquity of the ground is less than 15 degrees, there is no
appreciable error in the reading of the staff held in the ordinary way, and no
necessity for any correction on account of the excess of hypotheneusal over
base length. The ordinary correction for hypotheneusal over base distances
is marked on the link P, which is moved by the screw N, as in a theodolite.
The operation of survyeing with this instrument is as follows:-The
surveyor first sets out his base lines and lines of triangulation which he can
do with the telescope. The base line should of course be chained if it is
at all an extensive survey, and stakes driven at suitable and known points..

page_text: The instrument is then by means of a plumb bob set vertically over any of
these points. A sheet of paper is put on the table, and a line to correspond
with the base line of the survey marked on the sheet. This line by means of
the telescope is brought to coincide in direction with the base line, and the
table is then clamped by the clamp screw H. The staff men now take their
staves to the various salient points in the surrounding ground, such as A, B,
C, D, &c. (see Figure 5). The distances of these points from the instrument
at O are measured by means of the hairs in the eye-piece of the telescope, and
their direction corresponds with the direction of the telescope. When then
the distance (corrected if necessary for hypotheneusal excess,) is marked
along the scale L on the paper the point thus shewn is in the true position of
the reduced proportion of the scale to the ground. A line through these
points with a pencil completes the plotting of the survey. When the sur-
rounding fences, houses, roads, ponds, &c. have been observed the instrument
is moved on to the next station, and another paper put on, a note having been
previously made on the old paper of what portion of the survey it referred to.
The surveyor afterwards transfers all these detached portions of the survey to
his office plan by means of tracing, pricking through, or other device.
And having now described the nature of my said Invention, and in what
manner the same is to be performed, I declare that I claim the surveying
instrument constructed substantially in the manner and for the purposes
herein-before described and represented in the accompanying Drawings.
In witness whereof, I, the said David Reid Edgeworth, have hereunto
set my hand and seal, this 24th day of October, One thousand eight
hundred and sixty-six.
DAVID R. EDGEWORTH. (L.S.)