STANDARD - Survey Instrument Antique Center!

96
zero when plates are leveled up and that the bubble of the telescope level is in the
center of its graduation.
The, adjustment of Line of Collimation of Auxiliary Telescope : First examine the.
coincidence of the intersection of the cross wires with the optical axis. This may
be done by rotating the telescope in improvised wyes of wood (see p. 93), or by
rotating it in the socket of the pillar [as sometimes made by us] by unscrewing it
about one turn, when the adjustment is made by moving the capstan-headed screws
as described on page 58. The telescope must now be screwed to its bearing in such
a manner that the cross-wires are parallel to those of the main telescope to be verified
as explained in "To make the vertical wire perpendicular to the plane of the
horizontal axis," etc., p. 54.
To place the line of collimation of the auxiliary telescope in the same vertical plant
with that of the main telescope. Bisect a distant object with the vertical wire of the
main telescope ; see if the venical wire of the auxiliary telescope also bisects the same
point. If not, move the auxiliary telescope by means of the pair of opposing milledheaded
screws attached to its pillar nearer the eye-end until the distant object is
bisected at the same time by both vertical wires. Now focus the main telescope on a
near object and see if the vertical wire of the auxiliary telescope bisects the same
point as the vertical wire of the main telescope. If not, make the adjustment by
means of the pair of capstan-headed opposing screws on one side of the adjusting
trivets of the pillar. Then re-examine both wires for coincidence with the distant
object, u-ing the milled-headed screws, and also repeat the adjustment for near object
if necessary. The two lines of collimation are now in the same vertical plane.
To adjust the top telescope so that both horizontal wires bisect the same distant
object. Bisect a distant object with the horizontal wire of the main telescope, and see
whether the horizontal wire of the auxiliary telescope bisects the same point. If not,
make the coincidence by means of the pair of opposing capstan screws in the trivets
near the milled-headed screws. This being done, both these adjustments should be
verified and repeated if necessary. These adjustments once carefully made assure
the exact parallelism of both telescopes and will not require repetition except at long
intervals, or after an injury.
The distance between the lines of sight of the two telescopes should be carefully
measured by sighting at a vertical line on a wall the telescopes being horizontal
when the distance between the intersections of the two horizontal wires on the line will
be the eccentricity of the top telescope, for which every vertical angle measured with
it should be corrected.
The Berger Style I Interchangeable Auxiliary
Telescope (Patented).
See pages 189 and 193.
In this device Style I, the auxiliary telescope screws direct upon an open central
vertical post cast in one piece with the transverse axis to secure great rigidity, the
degree of accuracy of the result depending in a large measure upon the degree of
accuracy with which the center of the pillar, and the line of collimation of the principal
(then vertical) wire of the auxiliary telescope are made to lie in the same vertical
plane as the optical axis of the main telescope or parallel to it. With the care
given to it and special machinery used for it, this condition, difficultas it is, is secured
to an extent which leaves little to be desired for all practical purposes. As the aux-
iliary telescope is interchangeable from top to side there is really need of but one wire,
which we will designate as the principal wire. This, when the auxiliary is mounted
on top, is the vertical wire, and when on the side becomes the horizontal wire. Therefore
it will be seen that when the auxiliary is mounted on top the line of collimation
of its horizontal wire is immaterial, as no vertical angles will then be measured.
When the latter are to be measured the engineer will then mount the auxiliary on
the side, when in turn the vertical wire becomes immaterial. The auxiliary telescope
is provided with two milled-headed opposing screws for ranging in line with the
main telescope. The auxiliary telescope's adjustment of collimation and coincidence
of the cross-wires and optical axis must be verified by the use of improvised wooden
wyes (see above), should it become necessary.
The success which the interchangeable auxiliary telescope has achieved, both
here and abroad, since" first invented by this firm in 1895 is somewhat phenomenal.
It shows that this combination is the most applicable one in solving the difficult
problems arising in mine engineering. For this reason every preparation has been
made to meet the demand and new improvements are added as experience may suggest.
All our top telescopes are therefore now made interchangeable.