STANDARD - Survey Instrument Antique Center!

202
C. L. BEKGKK & SONS.
Flexible Jointed Ann with Magnifier
Attachable to Any of Our Transits for Keadiiig the Vertical and Horizontal Verniers
Code Word
The Adjustable Center
On Top of Transit Telescopes used Underground!,
Our transits are made mechanically so perfect
that the fine punch-mark provided on top of the
telescope, to enabl to center the instrument from a
point above, is seldom more than one to two hundredths
of an inch from the true center, without
any other device, and is generally considered sufficient.
But for cases where even this small eccen-
tricity is objected to, in mine and tunnel engineering
of a very precise character, we have devised ac
adjustable center, as shown in cut, to be attached
to the post (or if there is no post, to the top of the
Price, $7.5O
Hetide
telescope's axis, if same has been originally provided
with a stud to receive it when being made) by means
of which the center can be adjusted to be correct, enabling to set up the instrument undei
a given point so that the prolongation of the vertical axis of revolution of the transit be
truly in line with the plumb-bob hung from a point above, thus leaving nothing to be
desired. This operation can be very much simplified by the use of our lateral adjuster,
see page 205. When not needed, the adjustable center can be unscrewed and screwed
in the box. If a top telescope is to be used, the transit proper should first be set up
correctly under the given point. This done, the adjustable center can be removed and the
top telescope screwed in its Patented.
place. This device once properly adjusted to its transit by us
does not require any more attention in the future, unless the instrument should meet
with an accident, such as bending of the standards, or of the telescope's axis, etc., when
naturally, after it has been repaired, this adjustment of the centering device must again
be made.
Price of adjustable center
Code word
. $3.5O
. HetiUo