IMPROVEMENTS IN THE CONSTRUCTION OF LEVELS AND THEODOLITES
Year: 1865

page_text: PROVISIONAL SPECIFICATION left by John Coope Haddan at the
Office of the Commissioners of Patents, with his Petition, on the 23rd
December 1865.
I, JOHN COOPE HADDAN, of Bessborough Gardens, Pimlico, in the County
of Middlesex, Engineer, do hereby declare the nature of the said Inven-
tion for "IMPROVEMENTS IN THE CONSTRUCTION OF LEVELS AND THEODOLITES," to
be as follows:-
The object of the Invention is the so constructing levels and theodolites as
to afford facilities for ascertaining the more readily by experiment or trial
when they are out of adjustment, and for effecting adjustment when required,
and further the so constructing them that they shall without experiment or
trial (to be specially made) indicate whether they are or are not in
adjustment.
To ascertain whether an ordinary level is out of adjustment the usual plan
is to try with two staffs, first, setting the instrument midway between them
and then near to one staff, when, if out of adjustment the diaphragm carrying
the-hair line has to be moved, and repeated trials made to rectify the error,
the movement being effected by sinall screws (ordinarily capstan-headed
screws,) situate opposite to each other and required to be worked in pairs.
My Invention embraces the so making and adapting the diaphragm that it
may be turned round in the telescope without turning round the telescope
itself, so that if in observing a distant staff or object the hair line does not
cut or read to the same altitude it is at once evident that an adjustment is
required, and in providing for such adjustment by employing instead of each

page_text: pair of ordinary adjusting screws, one screw only, but the said screw in com-
bination with a spring opposite or otherwise placed with regard to it, so that
the screw on being turned in one direction may propel or push the diaphragm,
and on being turned or withdrawn in the contrary direction may allow the
diaphragm to follow it closely, being impelled so to do by the action of the
spring. It is to be understood that when cross hairs are employed, as in some
levels and in theodolites, and proper collimation is required both vertically and
horizontally combined, the diaphragm is to be made with a double action or
motion for adjustment, one at right angles to the other, each with one screw
and spring, and the diaphragm to be so made and adapted as that it may be
turned round in the telescope without turning the telescope itself.
With reference to the "further" object of making the instruments self-
indicating as to adjustment (that is. to. say, without special experiment or
trial) it will assist the definition of my improvements to note that in an ordinary
Troughton's level the bubble tube is a fixture to the telescope and requires no
adjustinent with reference to the line of collimation, while-in an ordinary. Y-
level and in an ordinary "dumpy" level this is not the case, but an adjustment
of this description is provided; and in all these a further and necessary
adjustment is provided, namely, that of placing the longitudinal axis of the
télescope perpendicularly to the vertical axis of the instrument, and which is
effected by means of the ordinary "plate" screws used in "setting" it. Now
to render the instruments "self-indicating" as above explained, my Invention
further embraces the employing two bubble tubes, both placed (or when in
use so that they may be both placed or become situate) longitudinally with
regard to or generally parallel to the axis of the telescope, the one a fixture
with reference to the telescope (except as herein-after set forth,) and the
other a fixture to the frame which carries the telescope, screw or
other
adjustments being furnished to regulate one relatively- to the other, and set
them parallel after regulating or levelling the frame by means of the ordinary
plate screws. The above referred to exception as to fixture of telescope
bubble tube to telescope is intended or may apply to Y-levels or such as
permit the telescope to turn round on its longitudinal axis in the bearings
which support it. In these cases instead of being an absolute fixture to the
télescope the particular bubble tube belonging to it should be made capable of
turning round on its own (the tube's) longitudinal axis in such manner that
the said axis may be permanently parallel to the longitudinal axis or line of
collimation of the telescope whenever the upper or graduated surface of the
bubble tube is presented upwards. My improved double bubble tubed instru-
ments, whether constructed with or without the exceptional condition as to
60

page_text: absolute fixture of one bubble tube to telescope, will it is evident after having
been once (and very easily) set for parallelism of the two bubble tubes require
this adjustment to be very rarely repeated, (perhaps only once a day or much
less frequently), but after any ordinary "setting" of the instruments when
using them they will be "self-indicating" (as to proper adjustment) by the
coincidence or non-coincidence of both bubbles being simultaneously at the
centres of their respective "runs," and which may be noted if desired every
time that the staff is read. Moreover, if a non-coincidence be noted the
error may be quickly remedied by the screw or other adjustments for regu-
lating the parallelism above referred to, and the surveyor will be spared the
ordinary very tedious process of repeated trials to ascertain whether an instru-
ment is or is not an adjustment, and when not in adjustment to bring it into
working order.
My Invention also embraces the construction of levels with two separate
diaphragms to be used in combination, each carrying a horizontal hair line
with or without a vertical hair line or lines, and each being made capable of
adjustment independently of the other, (the movement of the one not being
at right angles to that of the other). When both are in proper adjustment
for collimation the liues should coincide, and as it is extremely unlikely that
both would be simultaneously put out of adjustment to the same extent the
want of coincidence would immediately indicate to the observer when the
adjustment required attention. If to effect the adjustment one screw and
spring be used for each diaphragm as above set forth, it is desirable that
for one diaphragm the screw should be uppermost and the spring beneath,
and for the other diaphragm the spring should be uppermost and the screw
beneath.