Improvements in Surveying Instruments.
Year: 1891

page_text: Date of Application (in United Kingdom), 11th Nov., 1891
Complete Specification Left, 18th Feb., 1892-Accepted, 19th Mar., 1892
PROVISIONAL SPECIFICATION.
Improvements in Surveying Instruments.
1 JAMES ALBERT BROWN, of Wilmington, in the County of Clinton and State
of Ohio, United States of America, Civil Engineer do hereby declare the nature
of this invention to be as follows:-
This invention relates to theodolites, transits, levels, and other similar instruments
used in surveying, and it consists of a certain simplified construction of level for
levelling the same.
Beneath the telescope of the theodolite or transit mounted as usual is a long level
tube secured to the telescope parallel to the line of sight and containing a long
glass bubble-tube. At the top and bottom of the tube are two central slots to
shew the bubble and over each of these slots a graduated scale to indicate when
the bubble is in a central position. The brass tube has flat arms at the ends
which slip over screws rigidly attached to the telescope of the theodolite. The
said arms are held between nuts which are adjusted by capstan bars fitting in
holes in the nuts.
The function of the double, slot in the outer tube is to provide a means for
levelling the instrument when the barrel is revolved vertically through 180°, thus
providing against the necessity, for using two levels, one above and one below the
barrel of the instrument, or of unclamping the plates. This is specially desirable
when levelling work is being done.
Owing to inequalities in the wyes or in the glass tube, scale, or other parts of
the instrument, the central position of the bubble when the instrument is level and
the bubble tube under it is not necessarily in the same vertical line with the central
position of the bubble when the instrument is level and the bubble tube over it.
In other words, the two scales must each be independently adjusted for each
instrument. This would first be done at the instrument-makers' as follows-
Fasten the glass bubble-tube firmly in the long brass tube and rigidly fix a scale
over the upper slot. Attach the long tube to the telescope and in the ordinary
way make it parallel to the line of collimation. The bubble now being in the
centre of the scale, carefully observe the height on a levelling-rod. Turn the
telescope vertically through 180° and the upper parts of the instrument one-half
way around. The bubble is now at the opposite slot. Clamp the axis of the
telescope and bring the horizontal cross-line to the observed height, carefully mark
the position of the bubble and place over it a scale whose zero-line stands over its
central point. This scale may be rigid or capable of longitudinal adjustment. The
adjustment: Carefully level the plates, bring the bubble to the centre of one of
the scales, and observe the height on a levelling-rod. Turn the telescope vertically
through 180° and the upper parts of the instrument one-half way round, bring the
bubble to the centre of this opposite scale, and again observe the height on the
rod. If the two heights are the same, the long tube is in adjustment. If not
the same, turn the horizontal cross-line on a point midway between the two
observed heights, clamp the telescope in this position, and by means of the
capstan-nuts bring the bubble to the centre of the scale which completes the
adjustment.

page_text: I am aware that two tubes have been employed to do the work of the one
invented by me, but I claim that the use of a single tube with slots above and
below for the bubble, not only simplifies the construction and diminishes the cost
of the instrument but it also renders it more readily adjustable, more compact, and
generally more convenient.
1001
J. A. BROWN,
By A. M. & Wm. Clark,
53, Chancery Lane, London, Chartered Patent Agents.
COMPLETE SPECIFICATION.
Improvements in Surveying Instruments.
I, JAMES ALBERT BROWN of Wilmington, Clinton County, Ohio, United
States of America, 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:-
This invention relates to theodolites, transits, levels, and other similar instruments
used in surveying, and it consists in a certain simplified construction of level for
levelling the same which will be hereinafter described and claimed.
Reference is to be had to the accompanying drawings, forming part of this
Specification, wherein
Figure 1 represents a perspective view of a surveyor's theodolite fitted with
the improved level-tube.
Figure 2 represents a profile view of the improved level-tube, partly in section.
Fig. 3 represents a plan view of one form of level-scale.
The same reference letters indicate the same parts in all the figures.
A represents the telescope of the theodolite or transit, mounted as usual.
B represents a long level-tube preferably of brass, secured to the said telescope A
and parallel to the line of sight. In the interior of B is a long glass bubble-
tube B' secured in the usual way. At the top and bottom of the long brass tube B
are two central slots B2, B3 to shew the bubble and over each of these slots is a
graduated scale F to indicate when the bubble is in a central position. The
brass tube B has flat arms which slip over the screws C rigidly attached to the
telescope of the theodolite. The said arms are held between nuts D which are
adjusted with capstan-bars fitting in the holes d. The function of the double slot
in the tube B is to provide a means for levelling the instrument when the barrel is
revolved vertically through one hundred and eighty degrees, thus providing against
the necessity for using two level-tubes one above and one below the barrel of the
instrument or of unclamping the plates. This is specially desirable when levelling
work is being done.
Owing to inequalities in the wyes or in the glass tube, scale, or other parts of the
instrument, the central position of the bubble when the instrument is level and the
bubble tube under it, as shewn in the drawings, is not necessarily in the same
vertical line with the central position of the bubble when the instrument is level
and the bubble-tube over it. In other words, the two scales must each be
independently adjusted for each instrument. This would first be done at the
instrument-maker's as follows-Fasten the glass bubble-tube firmly in the long
brass tube and rigidly fix a scale over the upper slot. Attach the long tube to the
telescope and in the ordinary way make it parallel to the line of collimation. The
bubble now being in the centre of the scale, carefully observe the height on a
levelling-rod. Turn the telescope vertically through one hundred and eighty
degrees and the upper parts of the instrument one-half way around. The bubble
is now in the opposite slot. Clamp the axis of the telescope and bring the
horizontal cross-line to the observed height, carefully mark the position of the

page_text: bubble and place over it a scale whose zero-line stands over its central point. This
scale may be rigid or movable longitudinally, as shewn in Figure 3, where F
represents the scale and f slots for longitudinal adjustment, traversed by screws f¹
(Fig. 2).
The adjustment:-Carefully level the plates, bring the bubble to the centre of
one of the scales and observe the height on a levelling-rod, turn the telescope
vertically through one hundred and eighty degrees and the upper parts of the
instrument one-half way around, bring the bubble to the centre of this opposite
scale and again observe the height on the rod. If the two heights are the same,
the long tube is in adjustment. If not the same, turn the horizontal cross-line on a
point midway between the two observed heights, clamp the telescope in this
position and by means of the capstan-nuts bring. the bubble to the centre of the
scale, which completes the adjustment.
I am aware that two tubes have been employed to do the work of the one
invented by me, but, I claim that the use of a single tube with slots on either side
for the bubble not only simplifies the construction and diminishes the cost of the
instrument but it also renders it more readily adjustable, more compact and
generally more convenient.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is-
1. In an instrument for surveying, the combination, with a telescope, of a level-
tube secured thereto parallel to the line of sight said level tube having upper and
lower slots with a scale on cach slot for the bubble, substantially as described.
2. In an instrument for surveying, the combination, with a telescope, of a level-
tube connected to the said telescope by screws rigidly attached to the telescope
said tube having arms held between nuts moving on the said screws and having
upper and lower slots for the bubble with adjustable scales fitted to each slot,
substantially as described.
3. In a theodolite, the combination, with the telescope A having screws C rigidly
secured thereto, of the tube B enclosing a glass bubble-tube B' said tube B having
opposite apertures B2 and B³ for the bubble and arms and b' slipping over the
screws C, scales F having slots f for the screws f¹ secured over said apertures and
nuts D holding said arms b, substantially as described.
Dated this 18th day of Fohmiary 1800.
J. A. BROWN,
By A. M. & Wm. Clark,
53, Chancery Lane, London, Chartered Patent Agents.