IMPROVEMENTS IN INSTRUMENTS FOR MEASURING THE HEIGHTS AND DISTANCES OF OBJECTS
Year: 1875

page_text: LETTERS PATENT to Thomas Newnham Laslett, of No. 97, Maryon
Road, Charlton, in the County of Kent, Architect, for the Invention
of "IMPROVEMENTS IN INSTRUMENTS FOR MEASURING THE HEIGHTS AND
DISTANCES OF OBJECTS."
Sealed the 10th August 1875, and dated the 12th February 1875.
PROVISIONAL SPECIFICATION left by the said Thomas Newnham
Laslett at the Office of the Commissioners of Patents, with his
Petition, on the 12th February 1875.
I, THOMAS NEWNHAM LASLETT, of No. 97, Maryon Road, Charlton,
in the County of Kent, Architect, do hereby declare the nature of the
said Invention for "IMPROVEMENTS IN INSTRUMENTS FOR MEASURING THE
HEIGHTS AND DISTANCES OF OBJECTS," to be as follows:-
This Invention has for its object improvements in instruments for
measuring the heights and distances of objects.

page_text: three pins or feet fixed to one side of it or in a vertical position upon
three feet attached to one of its edges; all these feet are screwed for
adjustment, and the position of the instrument when in use is deter-
mined by spirit levels fixed to some convenient part of the plate.
One edge of the plate is segmental, and is marked with any required
scale, and at the centre from which the segment is struck is a pivot upon
which turns an index arm; such index arm is attached at one end to the
plate by the said pivot upon which it turns, and has at its free end a
finger for pointing to the various divisions of the scale.
Eyelet holes or a telescope are attached to the free end of the index
arm, the line of sight being directed from the free end of the arm to
the pivot. The telescope is furnished with a needle point in the focus
of the eye piece in place of the ordinary crossed hairs. A reflector is
fixed to the index arm exactly over the pivot at an angle of forty-five
degrees to the line of sight, and upon giving a small sliding motion to :
the telescope more or less of its view is covered by the reflector.
. The scales are made as follows:-At a convenient point in the
segment, to be called the zero of the scale, a tangent is drawn each way,
and the radius of the segment being taken as a unit or standard length,
equal divisions and subdivisions of it or other known dimensions relative:
to it are set out on the tangents beginning at zero, and upon lines being
drawn from these divisions on the tangents towards the pivot or centre
such lines will cut the segment at the points required for the scale.
The instrument is adjusted in a vertical position for use by means of
the screwed feet and the spirit levels, and the index finger being brought
to zero the index arm and the telescope will be vertical, and any object
seen through the telescope by reflection in the mirror will be on a level
with the pivot of the instrument.
When it is desired to ascertain the height of any object the top of
such object must be brought into view and into apparent contact with
the needle point by the index arm (which carries with it the telescope
and the reflector) being drawn backward or forward, when the reading
of the scale, multiplied by the distance of the object, will give its
height.
When it is desired to ascertain the distance of any object observations
must first be taken from the two extremities of a base line, bringing the

page_text: needle point into contact with the object each time, after which the
measurement of this base line, being divided by the difference of the
two readings, will give the required distance.
The advantages of my Invention are that the heights and distances of
inaccessible objects can be readily ascertained, whilst it admits of lineal
dimensions being used, and at the same time the needle point affords
great facility in taking observations.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Thomas Newnham Laslett in the Great Seal
Patent Office on the 12th August 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
NEWNHAM LASLETT, of No. 97, Maryon Road, Charlton, in the County
of Kent, Architect, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twelfth day of February, in the year of
our Lord One thousand eight hundred and seventy-five, in the thirty-
eighth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Thomas Newnham Laslett, Her special
license that I, the said Thomas Newnham Laslett, my executors, admi-
nistrators, and assigns, or such others as I, the said Thomas Newnham
Laslett, 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 Inven-
tion for "IMPROVEMENTS IN INSTRUMENTS FOR MEASURING THE HEIGHTS AND
DISTANCES OF OBJECTS," upon the condition (amongst others) that I, the
said Thomas Newnham Laslett, 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.

page_text: NOW KNOW YE, that I, the said Thomas Newnham Laslett, do
hereby declare the nature of the said Invention, and in what manner
the same is to be performed, to be particularly described and ascer-
tained in and by the following statement thereof, that is to say :-
This Invention has for its object improvements in instruments for t
measuring the heights and distances of objects.
For this purpose I proceed as follows:-I construct a plate or frame
standing in a horizontal position upon three pins or feet fixed to one side
of it or in a vertical position upon three feet attached to one of its edges;
all these feet are screwed for adjustment, and the position of the instru- 1
ment when in use is determined by spirit levels fixed to the telescope or
to some convenient part of the plate.
One edge of the plate is segmental, and is marked with any required
scale, and at the centre from which the segment is struck is a pivot,
upon which turns an index arm; such index arm is attached at one end 1
to the plate by the said pivot upon which it turns, and has at its free end
a finger for pointing to the various divisions of the scale.
Eyelet holes or a telescope are attached to the index arm, the line of
sight being directed from the free end of the arm to the pivot. The
telescope is furnished with a needle point in the focus of the eye piece in 2
place of the ordinary crossed hairs, but either the usual crossed hairs or
the needle point, or other similar contrivance may be used. A reflector
is fixed to the index arm exactly over the pivot at an angle of forty-five
degrees to the line of sight, and upon giving a small sliding motion to
the telescope more or less of its view is covered by the reflector, or the
sliding motion may be dispensed with.
Scales are made as follows:-At a convenient point in the segment to
be called the zero of the scale, a tangent is drawn each way, and the
radius of the segment being taken as a unit or standard length, equal
divisions and subdivisions of it or other dimensions relative to it are set
out on the tangents each way beginning at zero, and upon lines being
drawn from these divisions on the tangents towards the pivot or centre,
such lines will cut the segment at the points required for the scale.
The instrument being adjusted in a vertical position for use by means
of the screwed feet and spirit levels, and the index finger being brought
to zero, the line of sight of the telescope or eyelet holes will be vertical

page_text: and directed downwards, and any object seen through the telescope by
reflection in the mirror will be on a level with the pivot of the
instrument.
'
When it is desired to ascertain the height of any object the top of
such object must be brought into view and into apparent contact with
the needle point by the index arm (which carries with it the telescope
and the reflector) being drawn backward or forward when the reading
of the scale, multiplied by the distance of the object, will give its
height.
When it is desired to ascertain the distance of any object observations
must first be taken from the two extremities of a base line, bringing the
needle point into contact with the object each time, after which the
measurement of this base line, being divided by the difference of the two
readings, will give the required distance.
The advantages of my Invention are that the heights and distances of
inaccessible objects can be readily ascertained, whilst it admits of lineal
dimensions being used, and at the same time the needle point affords
great facility in taking observations.
The accompanying Drawings shew the arrangement of the several
parts of the instrument, but all or any of the said parts may be added to
or deducted from or varied in shape or size, and the materials of its
construction are such as are commonly used for making optical instru-
ments.
Having now particularly described the nature of my said Invention,
and the manner of performing the same, I would have it understood that
what I claim is, improvements in instruments for measuring the heights.
and distances of objects, substantially in the manner and for the purposes
herein-before described.
In witness whereof, I, the said Thomas Newnham Laslett, have
hereunto set my hand and seal, this Twelfth day of August, in
the year of our Lord One thousand eight hundred and seventy-
five.