An Improved Surveying Instrument and Stand for the same.
Year: 1891

page_text: Date of Application, 12th Dec., 1891
Complete Specification Left, 10th Oct., 1892-Accepted, 12th Nov., 1892
PROVISIONAL SPECIFICATION.
An Improved Surveying Instrument and Stand for the same.
I, LATIMER CLARK, of 11 Victoria Street, Westminster, Civil Engineer, do
hereby declare the nature of this invention to be as follows:
My improved stand is supported by three (or more) pairs of legs of the usual
construction. These legs support a ball and socket movement, the ball being
provided above with a screw attachment of the usual kind for the reception of the
level which it is desired to support.
The annular socket which surrounds the ball like a band embraces only about
one half the diameter of the ball, so that the latter can not only turn round freely
in the socket, but can also be easily inclined in any direction to a considerable
extent, and it is so arranged that it can be instantly clamped rigidly in any position
by tightening the socket upon it by means described below.
The socket is divided into three or more similar segments which when combined form
a horizontal ring fitting perfectly round the ball, and ground with concave surfaces
inside so that the ball moves smoothly in the socket thus formed. When completed
they are however each of them slightly shortened so that they become relatively
too small to embrace the ball and when strongly compressed upon it they no longer
allow it to turn freely but hold it rigidly. The annular segments have at each end
a lug projecting radially outwards from the ball, so that when they are in position
they form a ring with three pairs of vertical lugs in close juxtaposition, and these
being pierced with horizontal holes for the reception of bolts with wing-nuts, the
screwing up of the wing-nuts or of any one of them draws the segments together
tightly round the ball and causes it to be rigidly gripped. But the three bolts and
nuts do not pass through the lugs only, they also pass through holes in the pair of
wooden legs, which are of the usual split form joined together at the bottom. The
upper ends of these legs are placed outside the pair of lugs and come between
them and the wing-nuts, the result being that when the nuts are tightened the
pressure comes first on the legs, then on the pair of lugs between them, and lastly
upon the ball, and the screwing up of any one wing-nut compresses the whole
apparatus and renders not only the ball and sockets rigid but also the legs.
themselves.
The level to be supported is by preference fitted with a small circular level.
When used the legs are spread out without any particular regard to direction or
horizontality; the instrument is seized in the hands and turned round in the socket
to such a position that the levelling screws lie in the direction in which they are
intended to be used, while at the same time it is approximately levelled by the
circular level. In this position one turn of the nut makes the whole system rigid,
and the instrument only requires a slight final adjustment by the usual levelling
screws. A smaller subsidiary screw is provided between the segments which
only comes into tension when the wing-nuts are slacked out it then continues
to maintain such a tension on the segments as to produce a slight friction
between the ball and socket so that it is not perfectly loose but turns smoothly and
firmly.
I combine the system of measurement of distances known as Stadium measure-
ment with the ordinary surveyor's level. In this system a pair of horizontal webs
or wires is fixed in the focus of the telescope. On looking through the telescope at
a graduated staff and reading the number of feet subtended by the wires on the
staff, one can readily learn the distance of the staff, for the greater the distance,
the greater will be the number of divisions on the staff included between the two

page_text: horizontal wires. The distance they are fixed apart is usually such that whatever
be the number of divisions read on the staff the distance of tlie staff itself will be
just 100 times as great. For instance if the surveyor reads 2 36 feet on his
ordinary levelling staff, he knows that the staff is 236 feet distant from his
instrument.
This system can be applied conveniently in combination with the ordinary
surveyor's level, but I prefer not to have the pair of wires rigidly fixed in position
but to carry them in a vertical sliding frame, provided with a screw adjustment
outside beneath the eye-piece, so that they can be readily moved up and down in
the field of view. One of the two wires is thus easily brought over the zero line
on the staff, or any other even foot, and the distance read off on the second wire
gives the number of feet and decimals much more conveniently than if both wires
coincided with an odd number of divisions on the staff. The Stadium wires and
the levelling wires are carried by their frames extremely close to each other in
passing but never actually touch. They are however so nearly in the same plane
that both are seen in perfect focus together. One of the Stadium wires is
carried on an independent slide so that their distance apart can be at any time
adjusted.
When the operator is provided with a convenient means of measuring horizontal
distances directly by his level, it becomes desirable to give him also the means of
measuring horizontal angles, and I therefore form an instrument combining the
mechanism of the common level, with the adjustable stadium wires last described
for measuring distances, and with a graduated circle for measuring horizontal
angles. This combination gives an instrument not sensibly different from an
ordinary level in appearance and price but capable on occasion of fulfilling
many of the surveying purposes which are usually performed by the theodolite.
Dated this 12th day of December 1891.
CARPMAEL & Co.,
Agents.
COMPLETE SPECIFICATION.
An Improved Surveying Instrument and Stand for the same.
I, LATIMER CLARK, of 11 Victoria Street, Westminster, Civil Engineer, do
hereby declare the nature of this invention and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement :-
My improved stand is supported by three (or more) pairs of legs of the usual
construction. These legs support a ball and socket movement, the ball being
provided above with a screw attachment of the usual kind for the reception of the
level which it is desired to support.
The annular socket which surrounds the ball like a band embraces only about
one half the diameter or height of the ball, so that the latter can not only
turn round freely in the socket, but can also be easily inclined in any direction
to a considerable extent, and it is so arranged that it can be instantly clamped
rigidly in any position by tightening the socket upon it by means described below.
The socket is divided in one or more places and forms a horizontal ring fitting
perfectly round the ball, and ground with concave surfaces inside so that the ball
moves smoothly in the socket thus formed. The socket has lugs projecting
radially outwards from the ball and these are pierced with horizontal holes for the
reception of bolts with wing nuts. The bolts do not pass through the lugs only,
they also pass through holes in pairs of wooden legs, which are of the usual split
form joined together at the bottom. The upper ends of these legs are placed
outside a pair of the lugs and come between them and the wing nuts. The socket
is divided between two of the legs forming a pair the result being that when the

page_text: nut is tightened the pressure comes first on the legs, then on the pair of lugs
between them, and lastly upon the ball, and the screwing up of the wing nut
compresses the whole and renders the ball and socket and the leg rigid.
A smaller subsidiary screw is provided which only comes into tension when the
wing nut is slacked out it then continues to maintain such a tension as to produce a
slight friction between the ball and socket so that it is not perfectly loose but turns
smoothly and firmly.
Figure 1 illustrates a method of carrying this invention into effect and shows
a plan of the ball and socket movement together with portions of one pair
of legs.
Figure 2 is a side view of the same without the legs.
o represents a hole through the ball through which when required a plumb line
may be passed. pp represents a shoulder and screw upon the ball for the attach-
ment of the level, and represents as much of the ball as is visible in plan. It
works in a socket s.
ttare lugs cast on to the socket, and uu represents a portion of the ordinary
split legs of the stand. The ball is ground into the socket being held in
position by the annular plate s which is attached to the socket by screws, and
is ground to fit the ball at the same time as the socket to which it is screwed.
It is seen that the annular plate is completely divided at one point s', and this
division extends not only through the plate, but also through the socket itself, so
that by pressing the sides the socket can be sprung so as to press upon the ball rr
and hold it firmly. This pressure is applied by the thumb screw vv which is so
arranged that it not only tightens the leg of the stand, but by the same movement
causes the socket to grip the ball and to hold it firmly, making both the ball and
the stand perfectly rigid. It will be noticed that the other two pairs of lugs tt are
rigid and of the onlinary construction so that the tightening or loosening of their
thumbscrews has no influence on the ball and socket. If preferred the ring and
socket may have three clefts instead of one, in which case any one of the three
thumb screws will tighten up the whole system, but in practice the balance of
advantage is found in using only one division.
When the thumb screw v v is loosened the ball becomes comparatively free in its
socket and if unrestrained would be liable to fall about inconveniently. To obviate
this a small subsidiary screw is fixed in the lugs of the socket, and is marked to in
the drawing. The head is completely sunk in the lug and cannot come in contact
with the wooden legs; the tail is also too short to reach quite through. When
tightened up once for all, it is adjusted so as to maintain permanently a certain
comfortable strain on the socket, sufficient to prevent the ball from moving too
easily in its socket, when the pressure of the thuinb screw ev is removed.
The level has its own ball and socket movement and levelling screws of the
ordinary description; thus there are two ball and socket movements one over the
other. The level also is by preference fitted with a small circular level. When
the instrument is used the legs are spread out without any particular regard to
direction or horizontality; the instrument is seized in the hands and turned round
in the socket to such a position that the levelling screws lie in the direction in
which they are intended to be used, while at the same time the instrument is
approximately levelled by the circular level. In this position one turn of the
uute makes the whole system rigid, and the instrument only requires a slight final
adjustment by the usual levelling screws.
I combine the system of measurement of distances known as Stadium measurement
with the ordinary surveyor's level. In this system a pair of horizontal webs or
wires is fixed in the focus of the telescope. On looking through the telescope at a
graduated staff and reading the number of feet subtended by the wires on the staff,
one can readily learn the distance of the staff, for the greater the distance, the
greater will be the number of divisions on the staff included between the two
horizontal wires. The distance they are fixed apart is usually such that whatever
be the number of divisions read on the staff the distance of the staff itself will

page_text: be just 100 times as great.
ordinary levelling staff, he
instrument.
For instance if the surveyor reads 2.36 feet on his
knows that the staff is 236 feet distant from his
I prefer not to have the pair of wires rigidly fixed in position but to carry them
in a vertical sliding frame, provided with a screw adjustment outside beneath the
eye piece, so that they can be readily moved up and down in the field of view.
One of the two wires is thus easily brought over the zero line on the staff, or any
other even foot, and the distance read off on the second wire gives the number of
feet and decimals much more conveniently than if both wires coincided with an
odd number of divisions on the staff. The Stadium wires and the levelling wires
are carried by their frames extremely close to each other in passing but never
actually touch. They are however so nearly in the same plane that both are seen
in perfect focus together. One of the Stadium wires is carried on an independent
slide so that their distance apart can be at any time adjusted.
Figures 3, 4 and 5 refer to the arrangement of the Stadium wires. Figure 3
represents a section of part of the eye piece end of the telescope, omitting however
the eye glass and its supporting tube. a, a, represents the usual sliding plate
carrying the cross wires of a level, with its pair of capstan headed screws b, b,
behind by means of which the levelling hair of the telescope is adjusted. It
differs in nothing from the usual form except that the cross hair instead of being
carried on its face, is carried on a short tube c. c. which also carries the usual pair
of vertical hairs. I term this adjustable plate the "base plate."
Figure 4 d. d. represents a sliding frame with its guides e. e. which is attached to
the base plate this slide traverses freely up and down in its guides, being moved by
the milled head f with its ball and socket joint and its screw entering the slide d. d.
It carries the two Stadium hairs g g which are indicated by dotted lines, while the
three fixed hairs of the level are shewn by plain lines. The height of the short
tube cc (Figure 3) and the thickness of the slide d are so adjusted that the fixed
hairs, and the Stadium hairs are both almost in the same plane, there being only
just space enough for them to pass cach other without contact, so that both are in
focus at the same time. By turning the milled head either of the Stadium wires
is readily adjusted on any given foot on the levelling staff, and the distance is
easily read on the staff from one wire to the other. They are usually adjusted at
such a distance that one foot on the levelling staff corresponds to 100 feet of
horizontal distance, measured from the front of the object glass. In such case it is
necessary that the distance of the Stadium hairs apart should be one hundredth
part of the focal length of the object glass.
As it is extremely difficult to fix these hairs with sufficient accuracy for practical
purposes it becomes desirable to have some means of adjusting their distance from
each other after they are fixed. This is effected by the arrangement shown in
Figure 5 which represents the slide d d as shown in Figure 4 but contains some
additional details not given in the first figure. It will be seen in Figure 5 that the
slide dd itself carries a smaller slide i, i, which extends for only half its length, and
is adjustable by means of the screw & which has a square head and is turned by a
key when necessary. This screw is not a plain screw but a differential screw
having two threads of different pitches so as to give an extremely small movement
to the slide i i. The lower Stadium hair is fixed on the slide d d but the upper
hair is fixed on the shorter slide ii as shewn on the figure, and its distance
from the lower hair can be adjusted by the differential screw k.
In this figure
the two Stadium hairs only are shown (by dotted lines) the level hairs being
omitted.
When the operator is provided with a convenient means of measuring horizontal
distances directly by his level, it becomes desirable to give him also the means of
measuring horizontal angles, and I therefore form an instrument combining the
mechanism of the common level, with the adjustable Stadium wires last described
for measuring distances, and with a graduated circle for measuring horizontal
angles. This combination gives an instrument not sensibly different from an

page_text: ordinary level in appearance and price but capable on occasion of fulfilling many
of the surveying purposes which are usually performed by the theodolite.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is
1. A levelling stand substantially as described with a ball and socket for
supporting the level, such socket being divided at one or more points and having
lugs to which legs are connected; the whole so arranged that the force applied
to a thumb screw for tightening the legs of the level is transferred to the ball
and socket, so that all these parts are rendered rigid by one movement.
2. The combination of a level and stand substantially as described so that by
means of a ball and socket movement and clamp upon the stand the telescope
may be set roughly level and the whole locked fast, and that afterwards the
correction necessary may be made by the usual levelling movement of the
instrument.
3. The arrangement substantially as described of the webs or wires of the level
so that the Stadium wires are readily adjustable to any given mark on a levelling
staff, to facilitate the reading of the distances as given by the staff.
4. A level with Stadium webs or wires and with the said webs or wires adjustable
in their distance apart by the means described and shewn.
Dated this 7th day of October 1892.
LATIMER CLARK.