IMPROVEMENTS IN APPARATUS OR INSTRUMENTS FOR MEASURING DISTANCES AND ELEVATIONS
Year: 1857

page_text: LETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn Fields, in
the County of Middlesex, and of 166, Buchanan Street, in the City of
Glasgow, North Britain, Gentleman, for the Invention of "IMPROVEMENTS
IN APPARATUS OR INSTRUMENTS FOR MEASURING DISTANCES AND ELEVATIONS."— .
A communication from Enoch A. Crandall, of Friendship, Alleghany
County, in the State of New York, United States of America.
Sealed the 21st April 1857, and dated the 25th February 1857.
PROVISIONAL SPECIFICATION left by the said John Henry Johnson at
the Office of the Commissioners of Patents, with his Petition, on the
25th February 1857.
I, JOHN HENRY JOHNSON, of 47, Lincoln's Fields, in the County of
Middlesex, and of 166, Buchanan Street, in the City of Glasgow, North
Britain, Gentleman, do hereby declaro the nature of the said Invention for
"IMPROVEMENTS IN APPARATUS OR INSTRUMENTS FOR MEASURING DISTANCES AND
ELEVATIONS," a communication from Enoch A. Crandall, of Friendship,
Alleghany County, in the State of New York, United States of America, to
be as follows:-
This Invention relates to an improved instrument for measuring distances
by optical observations alone without the aid of a measuring chain or tape.
The instrument consists of a rectangular oblong hollow box, which serves as

page_text: the base plate, and which carries at each end a telescope, or other similar
sighting instrument. One of [these telescopes is fixed in such a manner that
it cannot be moved horizontally, but has its line of sight always at right angles
to the length of the base. It may, however, be fitted with a graduated circle
and turn vertically in bearings, for the purpose of measuring altitudes, if
desired. The opposite telescope or sighting instrument is made to turn
horizontally on a pivot, so that its line of sight may be made to intersect
the line of sight of the fixed telescope at any desired distance from the
instrument. The operation of this instrument is based upon the well-known
principle in trignometry, that when the length of the base (which in this
case is represented by the length of the oblong box, or the distance between
the axes of the two telescopes) of a right-angled triangle is given, the
adjacent angle formed by the hypotheneuse (which is the angle of the
moveable telescope) serves to determine the length of the perpendicular,
namely, the distance from the object to the observer along the line of sight of
the fixed telescope.
The turning of the moveable telescope, so as to bring it on to the object,
brings successively into play a series of indicating levers, which point out on
suitably divided scales the distance of the object from the observer. These
levers are arranged so as to multiply the slight movement imparted to them,
and thereby enable great distances to be read off from the scales with facility.
When used for ordinary surveying purposes, the box or base may be fitted
with the usual appurtenances, such as a compass, spirit level, and tripod.
In some cases, such as where the instrument is desired for facilitating the
navigation of vessels, near the coast for example, the moveable telescope is dis-
pensed with, and a reflector substituted, which will throw the image of the
object on to a similar reflector in the fixed telescope.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said John Henry Johnson in the Great Seal Patent Office on the
25th August 1857.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
and of 166, Buchanan Street, in the City of Glasgow, North Britain, Gentle-
man, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-fifth day of February, in the year of our Lord

page_text: One thousand eight hundred and fifty-seven, in the twentieth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said John Henry Johnson, Her special license that I, the said John Henry
Johnson, my executors, administrators, and assigns, or such others as I, the
said John Henry Johnson, my executors, administrators, or 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 "IMPROVE-
MENTS IN APPARATUS OR INSTRUMENTS FOR MEASURING DISTANCES AND ELEVATIONS."
a communication from Enoch A. Crandall, of Friendship, Alleghany County,
in the State of New York, United States of America, upon the condition
(amongst others) that the said John Henry Johnson, by an instrument
in writing under my hand and seal, 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 Henry Johnson, 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, reference being had to the accompanying Drawings, and
to the letters and figures marked thereon, that is to say:―
The said Invention relates to an improved instrument for measuring dis-
tances by optical observations alone without the aid of a measuring chain or
tape. The instrument consists of a rectangular oblong hollow box, which
serves as the base plate, and which carries at each end a telescope, or other
similar sighting instrument. One of these telescopes is fixed at right angles to
the axis of the box, and in such a manner that it cannot be moved horizontally
separately from the box to which it is attached. It may, however, be fitted
with a graduated circle and turn vertically in bearings, for the purpose of
measuring altitudes if desired. The opposite telescope or sighting instrument
is made to turn horizontally on a pivot, so that its line of sight may be made
to intersect the line of sight of the fixed telescope at any desired distance from
the instrument. The operation of this instrument is based upon the well-known
principle in trigonometry, that when the length of the base (which in this case
is represented by the oblong box, or the distance between the pivoting point of
the horizontally moveable telescope and the nearest point of the opposite
telescope, of a right-angled triangle is known, together with the adjacent angle

page_text: of the hypotheneuse and the base, the length of the perpendicular, namely, the
distance from the object to the observer along the line of sight of the fixed
telescope, can be easily deduced.
The turning of the moveable telescope, so as to bring it on to the object,
brings successively into play a series of indicating levers, which point out on
suitably divided scales the distance of the object from the observer. These
levers are arranged so as to multiply the slight movement imparted to the
telescope, and thereby enable great distances to be read off from the scales
with facility. When used for ordinary surveying purposes, the box or base
may be fitted with the usual appurtenances, such as a compass, spirit level,
and tripod.
In some cases, such as where the instrument is desired for assisting in the
navigation of vessels, near the coast for example, the moveable telescope is
dispensed with, and a reflector substituted, which will throw the image of the
object on to a similar reflector in the fixed telescope.
And in order that the said Invention may be fully understood, I shall now
proceed more particularly to describe the same, and for that purpose I shall
refer to the several Figures on the Sheet of Drawings hereunto annexed, the
same letters of reference indicating corresponding parts throughout all the
corresponding figures.
Figure 1 of the Drawings is a side view of the instrument; Figure 2 is a
plan of the same, with a portion of the top plate of the hollow box serving as
the base, broken away to show the interior; Figures 3 and 4 are diagrams, to
illustrate the operation of the instrument.
A is a rectangular box, forming the horizontal table or base of the instru-
ment; B is a telescope or sighting tube placed on a stand B' at one corner of
the box A, and arranged to be capable of receiving motion on a centre in a
vertical plane on trunnions b, b, fitted to bearings in the stand B'; C is a
second moveable telescope or tube carried by a stand similar to B', but-free to
turn horizontally on a pivot c in the base. The centre of this pivot-c-forms
the termination of the right line a, which is the base line on which all the
measurements are founded, and which must be exactly at right angles to the
axis of the telescope B. The telescope C is also arranged to turn vertically
on trunnions b, b; D is a horizontal index bar carrying an index 1, and
attached to the stand C¹ of the telescope C, in such a manner that when the
telescopes are parallel, the said index bar will be parallel to the side a, a, of
the base A. The index 1 works on a graduated scale of distances e, e¹; on
the face of the top plate of the base of the instrument. This index is furnished
with a screw clamp G, by which it is attached at pleasure to a screw H, so

page_text: that by turning the screw H, the telescope C will be partially revolved in a
horizontal plane, and adjusted with accuracy in any desired position. The
base of the instrument which can be attached to a tripod, similar to other
surveying instruments, is to be furnished with a horizontal limb, a compass,
and spirit level; but as the use of these is well understood and forms no part
of this Invention, I have not considered it necessary to shew them. In.
connection with the index bar D and its index 1, I use a system of multiplying
levers and scales to multiply the scale of distances as I shall hereafter
describe.
By way of shewing the use of this instrument, let it be supposed that the.
distance from B to T (Diagram, Figure 3) is to be measured. A staff is placed
at the point T, unless some object already stationary at that point be used as a
sight point. The instrument is placed with the axis of the stand B (Figures 1
and 2) on the point B (Figure 3), and with the tube B sighted to the point T.
The line a of the instrument then forms a base, to which the line B, T, is per-
pendicular. The tubo C is then turned on its pivot c at the end of the line a,
until it also sights the point T, and the length of the base a being constant,
the angle that is formed at C serves to determine the length of the perpen-
dicular B, T. The index D moves with the telescope C, so that the scale e, e¹,
being graduated in distances corresponding to the varying angles at C, the
true distance from B to T is indicated by the index on the scale e, e'. The
spaces between the graduations on the scale e, e', diminish according to a
certain law at one extremity of the scale. In measuring long distances, C
stands nearly parallel with B, and as they approach a state of parallelism tho
prolonged axis of C or the line C, T, will take a long range along the line B, T,
without producing any very perceptible movement in the index. This renders
it impossible that the scale e, e', the width of whose gradations diminish
progressively from the commencement, can either be graduated, or read up to
a termination at the end e', with so great a degree of exactness as is desirable
for precise measurement. It is with a view to remedy this deficiency that I
have added to the instrument the multiplying levers, and the additional scales,
which I will now proceed to describe.
The multiplying levers, of which I have shown three J, K, L, but of which
there may be any other number, are all arranged to work within the box or
hollow base A, so as to be out of the way of the surveyor, but are furnished
respectively with indices 2, 3, and 4, working through slots in the top plate of
the base over their respective graduated scales o, o¹, p, p, q, q', on the upper
surface of the plate. The lever J, which is the first of the series, is a lever of
the first order, working on a fulcrum j, and has a long and a short arm, the,

page_text: index 2 being attached to the long arm j", whilst the short arm is fitted at
its extremity with a roller or shoc, or it is made of a pointed or rounded form,'
and is so placed relatively to the index bar D, that when the index 1 has
moved far enough up the scale e, e', to afford accurate indications, an arm d
on the bar D comes in contact with the end of the short arm of the lever J,
and by a continuous movement of the bar D towards the line a, a, the lever J
is put in motion, and the index 2 is caused to move over the scale o, o'.
The scale o, o, is graduated to suit the movement of the index 2, the spaces
between each graduation bearing the same proportion to the corresponding.
gradations on the index e, e', as the rate of motion of the index 2 bears to that
of the index 1. The lever K carrying the index 3, working over the scale p,p',
is placed on a fulcrum k, and is similar to the lever J, except that its long
arm, carrying the index, is so proportioned to the short arm k¹, that any
motion of the index bar D causes a greater movement of its index than that
of the index 2. It is operated upon by a second arm d' on the index
bar D, but the parts are so proportioned that it is not touched till the index 2
approaches near to the end o¹ of its scale, where the divisions become very
minute. The lever L, carrying the index 4, may be similar to the lever K,
except that there must be a still greater difference in the lengths of its long
and short arms; or it may be arranged as represented in the Drawing. The
effect in either case is to multiply the slight motion of the index bar in some
great and unchanging ratio. As represented in the Drawing, it works on a
fulcrum l, over the scale q, q', near the opposite end of the base A, and derives
its motion from the lever K, at a point near the index 3. When the index 8
arrives near the end p¹ of its scale, the lever K comes in contact with the short
arm of the L, and gives an increased motion to the index 4.
The levers J, K, L, bave severally applied to them springs V, V, to throw
their indices back to the commencement of their respective scales, when the
bar D is moved away from the edge of the base A. By an arrangement of
multiplying levers and scales, such as I have described, a sufficient motion of
the index may be obtained to show the movement of the telescope C to any
desired point in the line of sight of the telescope B. The three levers pro-
portioned, as shewn in the Drawing, multiply the scale one hundred times; to
multiply the motion to the same extent, with the indices all in operation tho
whole time, would compel the quickest indices to make more than a complete
revolution, and would thus confound the graduation, or else would require so
much room as to be almost useless in practice; but by arranging the indices to
come successively into operation, each as the graduation of the scale of its
predecessor become too small to be easily distinguishable, the multiplication is

page_text: not effected till it becomes requisite, and the separate indices are caused to
require only a short range.
The graduating of the scales o, o', p, p, and g, g', is easy when the rate of
motion of the respective indices 2, 3, and 4, relatively to that of index 1, is
known, the proper points for graduations on the scale e, e', may be mathe-
matically ascertained by the aid of sufficiently full tables of natural tangents,
or by any other well-known means of ascertaining exactly the relations
between angles and their tangents; the complements of the angles B, C, T,
Figure 3, formed by bringing the telescope to bear on points at all the various
distances to be measured, are the quantities practically required to be ascer-
tained previous to commencing the process of graduation. When the
telescope C is absolutely parallel to the telescope B, the index 1 stands at a.
certain point on the scale e, e', which may be marked co to indicate an infinite
distance, and the angular distances therefrom of all the other graduations are
ascertained by the following process:-Assuming the length of the line a to be
exactly one foot, cach distance which it is desired to measure must be reduced
to feet. The number thus found is the cotangent of a certain angle, which
angle must be found by the table or otherwise, and laid off as accurately as
possible on the scale e, e', starting in every case at the point co. The proper
amount of each angle for the scale e, e', being thus ascertained in degrees,
minutes, seconds, and parts of seconds, the same must be multiplied in the
proper ratio for each of the other scales, as already described.
'
All the working or contact surfaces, or in other words the surfaces, which
act on and give motion to the levers, must be attended to with great care. If
the fulcrums j, k, are placed as in the Drawing, the point of contact will
change somewhat as the levers move, that is, to the extremities ³, k³, will
slide on the faces of d, d', and the said faces must, by patient trial or other-
wise, be finished in such a curve as will result in imparting to the levers.
motions which bear unchangeable ratios to that of the index bar D. Any
other form may be adopted, however, if in the graduations thero be due
allowance made for the inequalities in the motions.
In constructing the instrument for some purposes, for example, to facilitate
the navigation of vessels near a coast, the telescope C may be dispensed with,
and a reflector substituted which will throw the image of the object upon a
similar reflector in the telescope B. When thus arranged the observer may
hold the instrument in his hand, sighting through B alone, and turning the.
screw H until the image due to the reflector is directly over, or directly.
under, or directly coincident with that seen through the glasses, it being
then ased similar to the ordinary sextant.

page_text: From the foregoing explanation it will be seen that operation of the
instrument is extremely simple and easily comprehended, but in order to avoid
errors arising from the elasticity or loss of motion of the parts, it is necessary
always to move the indices along their respective scales by a positive motion,
as the springs V, V, should not be depended on to act with the exact force
required. In careful measurements, therefore, the instrument should first bo
set to indicato a less distance than that to be measured, and the distance
indicated should then be increased by small increments until the telescope C
ranges exactly at the point desired. Any derangement, occurring in the action
of any lever, is readily detected by its indications disagreeing with those of the
others. When perfect, the indices 2, 3, 4, and as many more as may be
added, must all agree in their indications of perfect parallelism, and also of
such distances as may chance to be graduated on any two or more scales.
The position of the cross wires in the telescope C may be charged slightly by
means well-known to instrument makers, so as to counteract the effect of
accident; or of varying temperatures, in changing the length of the base a, a.
In measuring long distances it may be advisable, in some instances, prac-
tically to increase the length of the base a, a, by making an offset of any
convenient length. In operating in this manner, the telescope B is first
sighted at the object, then the whole instrument is transferred bodily to a new
position at the extremity of the offset, and the telescope B is placed parallel to
its first position, or in the line W, Z (Fig. 3). Tho telescope C being next
brought to bear on the object T, the distance indicated by the indices must be
multiplied by the amount of the offset in feet, plus one; the product is, the
true distanco B, T. A similar result may be obtained at one observation by
employing a horizontal rod in the hands of the staff holder, as represented in
Fig. 4, where B, a, C, represents the actual width of the instrument; B, T,
tho distance to be measured, and U, T, the rod referred to. A staff being
fixed on each end of this rod, and the rod being of a determinato length, ninc
feet for example, and fixed by any well-known means in a position at right
angles to the line B, T, the telescope B is sighted at T, and the telescope C
sighted at U. Under these circumstances the distance indicated on the scales
being multiplied by the length of the rod U, T, in feet, plus one, the true
distance desired is obtained.
-
The distances indicated by this instrument are measured in a horizontal
plane, that is, the instrument indicates the absolute distances to point on its
own level, directly above or below the object T. I attach to the telescope B,'
a circlo M, described from the trunnions b, b, and graduated on a part of its
circumference in degrees and minutes, and provide a stationary index or

page_text: vernier N as represented, so that when both the angular attitude of an object,
and its horizontal distance from the point of observation, have been thus
indicated, the difference in level in feet may be readily ascertained by the aid
of proper tables, which are intended to accompany such instrument.
Having now described and particularly ascertained the nature of (the) (my)
(our) said Invention, and the manner in which the same is or may be used
or carried into effect, (I) would observe, in conclusion, that (1) do not
confine or restrict (myself) to the precise details or arrangements, which
(I) have had occasion to describe or refer to, as variations may be made
therefrom without deviating from the principles or main features of (the)
said Invention; nor do I claim any of the mechanical elements, of which the
said apparatus and parts of apparatus are respectively composed, as being
separately or apart from the use or application of such elements to form the
combinations, constituting such apparatus and parts of apparatus respectively,
as being any part of my said Invention; but what I consider to be novel and
original, and therefore claim as the Invention secured to (me) by the herein-
before in part recited Letters Patent, is,―
The general construction, arrangement, and combination of apparatus,
forming an instrument for measuring distances and elevations, as hercin-before
described.
In witness whereof, I, the said John Henry Johnson, have hereunto set
my hand and seal, this Twenty-fourth day of August, One thousand
eight hundred and fifty-seven.