A NEW OR IMPROVED TOPOGRAPH
Year: 1865

page_text: LETTERS PATENT to Auguste Frederic Lendy, of Sunbury, in the County
⚫ of Middlesex, for the Invention of "A NEW OR IMPROVED TOPOGRAPH."
Sealed the 4th July 1865, and dated the 11th January 1865.
PROVISIONAL SPECIFICATION left by the said Auguste Frederic Lendy at
the Office of the Commissioners of Patents, with his Petition, on the
11th January 1865.
I, AUGUSTE FREDERIC LENDY, of Sunbury, in the County of Middlesex, do
hereby declare the nature of the said Invention for "A NEW OR IMPROVED.
TOPOGRAPH," to be as follows:-.
This Invention relates to a new or improved topograph for the purpose of
surveying, and combines in one instrument everything necessary for the ac-.
complishment of such work. It consists of a plane table, made of a small.
square of wood or metal, having recesses cut on its surfaces for the reception.
of the different parts of the instrument. On the upper surface a layer of paper
is fixed on a centre so as to be capable of being turned to the various requisite
angles for drawing plans. The paper is ruled in small squares throughout its.
surface for facilitating accurate drawing. The edge of the plane is provided:
with a sight ruler, and a level capable of adjustment by a set screw is also
attached. A compass is likewise set in a recess on the upper surface of the
plane.

page_text: The topograph may be used, firstly, as a prismatic compass alone; secondly,
as a plane table alone, with its sight ruler; thirdly, as a plane table and a
compass combined to facilitate the finding of stations; fourthly, as a level;
fifthly, as a clinometer to obtain angles of elevation or depression, to find the
difference of altitude of two stations, and to lay down contours, all combined
in one. The instrument possesses that great advantage that it may be used
without any alteration simultaneously or successively as a plane table or a
compass when in the same survey one passes from accidented ground to open
country, and vice versa.
In all cases there is no need of scales, or pair of compasses, or protractor,
the apparatus itself protracting the angles and laying down distances at the
scale.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Auguste Frederic Lendy in the Great Seal Patent Office on
the 7th July 1865.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, AUGUSTE
FREDERIC LENDY, of Sunbury, in the County of Middlesex, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Eleventh day of January, in the year of our Lord
One thousand eight hundred and sixty-five, in the twenty-eighth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said Auguste Frederic Lendy, Her special licence that I, the said Auguste
Frederic Lendy, my executors, administrators, and assigns, or such others as I,
the said Auguste Frederic Lendy, 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 OR IMPROVED TOPOGRAPH," upon the condition (amongst others) that the, the
said Auguste Frederic Lendy, my executors or administrators, by an instru-
ment 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 imme-
diately after the date of the said Letters Patent.

page_text: NOW KNOW YE, that I, the said Auguste Frederic Lendy, 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
following statement :-
The improvement relates to the construction of a surveying instrument,
called topograph, intended to enable any one, however unacquainted he may
be with mathematics, to become in a few minutes capable of surveying a road,
sketching a country, finding the heights of buildings and mountains, &c. ; to
enable those who already possess a knowledge of surveying to survey almost
as rapidly as they walk; finally, to enable those who are acquainted with
geometry to represent with accuracy the features of the ground in whatever
districts they may find themselves.
The topograph is at the same time a drawing board, a plane table, a prismatic
compass, a level, a clinometer, and dispenses with the use of scales, protractors,
and compasses. The topograph may be used 1, as a prismatic compass alone;
2, as a plane table alone, with its sight ruler; 3, as a plane table and a com-
pass combined to facilitate the finding of stations. It possesses that great
advantage that it may be employed without any alteration, simultaneously or
successively, as a plane table or a compass when in the same survey we pass
from undulating ground to open country, and vice versa.
In all cases we need no scales, no pair of compasses, and no protractor, the
machine itself protracting the angles and laying down distances at the scale.
Again, the topograph may be used, 1, as a level; 2, as a clinometer to
obtain angles of elevation or depression, to find the difference of altitude of two
stations, and to lay down contours. The topograph may be of any size and of
any material; its use and properties are described as follows:-
Paper. The paper used with this instrument should be transparent. A thin
paper does not bear india-rubber, suffers much from moisture, and is easily
torn. The best material is what is sold under the name of tracing paper,
No. 12. It is a transparent fabric, linen or calico, coated with paper; it
stands rubbing, cannot be torn, and is not easily spoilt by rain.
Fixing the paper.-The paper is stretched on the board by means of the
four grapples a, which are kept tight by strong springs.
Prismatic compass.-The topograph is held in the left hand by the handle H.
The prism A and the sight vane B being raised to their proper positions we
take bearings as usual by turning the left hand until the object is seen through
the slit in coincidence with the thread of the vane. The vibrations of the
card are checked by pressing on the springs, and the graduation that corre-
sponds to the thread gives the required azimuth.

page_text: . To protract the bearings.-The circular protractor attached to the upper
surface of the board has its circumference divided into 360 degrees, and bears
two graduations, one in black, the other in red. The circle is ruled over by
two systems of parallel lines at right angles to one another. The lines parallel
to diameter 90270 are red, and at intervals representing 20 paces on the
scales of 8 inches to the mile every fifth line being made thicker to facilitate
the reading. The black lines parallel to diameter 360-180 are at intervals
representing 20 paces on the scale of 6 inches. To trace a direction,
azimuth of which has been found to be 40°, for instance, we turn the screw U
with the thumb and forefinger of the left hand until the black graduation 40
comes under the index I. All the black lines of the circle are now parallel to
line Q1 representing the magnetic meridan. To
draw the direction, we trace with the pencil the black line passing through
the point of station. The distance paced in that direction, 120 paces for
instance, is laid down by marking across six intervals of the red lines. Should
we require a survey on the scale of 6 inches to the mile, we protract the bear-
ings with the red graduation and lay the distances along the red lines across
the requisite number of black intervals.
the direction required, the
Scales. By assuming the divisions to represent 40 or 10 paces, we obtain
the additional scales of 3 inches, 4 inches, 12 inches, and 16 inches to the
mile. The circular board being moveable, other scales may be used if
required.
Plane table. When the topograph is to be used as a plane table we still
hold it in the left hand. The sight ruler is removed from its scabbard R, R,
and is inserted in the grooves g, g; it is thus prevented from falling, a dis-
position readily appreciated by those who have to survey on horseback. When
the ruler has been turned to its proper position it is secured by its screw, and
the required direction is then easily drawn. Distances are laid down as before
by means of the protractor.
Plane table and compass.-When using the plane table stations are easily
found with the assistance of the compass. For that purpose the opening C, D,
corresponds to an angle of more than 90 degrees; in whatever position, there-
fore, the instrument may be turned, one of the four radii, N., E., S., W., must
fall within that opening, and an index k, moveable by the screw b, can be
placed exactly opposite to that radius. In all the above cases the instrument
can be used with a tripod whenever great precision is necessary.
Clinometer. The clinometer consists of two semicircles, a fixed one and a
moveable one. The fixed semicircle is pasted to the board with its diameter
exactly parallel to A, B; its surface is divided into zones of equal width by

page_text: vertical lines graduated from the centre to the right and left. A second series
of equidistant lines are drawn parallel to the diameter, and are graduated down-
wards. The moveable semicircle, is made of metal; its diameter is divided
into parts corresponding exactly to those of the fixed one, and its circumference
is divided into 90 degrees on each quadrant. The moveable diameter carries
two small pins projecting outwards, and on the prolongation of the fixed
line we find two holes o, o', right through the length of the board in exact
parallelism with A, B.
To find a level line. To obtain a horizontal line hold the instrument ver-
tically with the left hand, and look through the hole o, when the hole o¹ and
the two pins v, v', come in line, the direction o, o¹, is horizontal.
Angles of elevation.-To take angles of elevation or depression hold the in-
strument in the same manner, and look through the hole o until the object
appears at the intersection of the hairs in o¹, pressing at the same time on the
spring p, which fastens the protractor. The spring being set free, the angle
required is marked by the index y.
Vertical distances.-The difference of altitudes between the stations are readily
found. If stationing at one point the angle of elevation of another is for in-
stance 25°, and the horizontal distance furnished by the plan 290 yards, the
difference of altitudo is obtained by taking division 29 of the fixed diameter,
and following its vertical until it intersects the moveable diameter. The hori-
zontal passing through the point of intersection is 18, and therefore the
difference required is 135 yards.
Reduction of distances to the horizon.-To reduce to the horizon a distance
measured along a slope, turn the brass semicircle until the index points to the
angle of elevation. The divisions of its diameter represent the distances
actually measured, whilst the verticals passing through these divisions point on
the fixed diameter to their horizontal projections. Thus, if the distance
measured is 530 yards, and the angle of elevation 20°, the horizontal distanco
is 498 yards.
Contouring. Let us suppose that in a survey contours are wanted 10 feet
vertically apart. We begin, as in the ordinary process, by tracing one contour
on the ground and then on the paper, an operation which the level o, o³, will
render easy.
We then station on that contour, at some convenient point
belonging to a ridge, a tholweg or a regular slope, and take the angle of
elevation or depression. The parallel 10 intersects the moveable diameter,
and the vertical passing through this point of intersection gives on the fixed
diameter the horizontal distance between the contours. If the angle of
depression is 17° the contours along the uniform slope should be 33 feet apart

page_text: on the plan. If great precision is required, the topograph is carried on a tripod
of the ordinary construction (socket and ball), which is screwed to hole Y.
In witness whereof, I, the said Auguste Frederic Lendy, have hereunto
set my hand and seal, this 5th day of July, in the year of our Lord
One thousand eight hundred and sixty-five.