Year: 1887

page_text: Date of Application, 4th May, 1887.
Complete Left, 5th Aug., 1887.
Complete Accepted, 6th Sept., 1887.
I, FRANCIS ST. George CaulfEILD Civil Engineer of The Manor House Earley
Reading Berkshire, and Taipeng Larnt Penang Straits Settlements do hereby declare
the nature of this invention to be as follows:-
The attachment of the diaphragm and cross lines and such portions of the instrument
as come between it and the eye of the observer to a piece of tube, made to fit the end
of the sliding tube in which the diaphragm is usually fixed, and easily withdrawn
therefrom, and reversible therein; in much the same manner as the eye piece of such
instruments is usually attached, and with such studs and slots as may be necessary for
accurate reversion and replacement.

page_text: COMPLETE SPECIFICATION.
An Improvement in Levelling and Surveying Instruments.
I, FRANCIS ST. GEORGE CAULFEILD, Civil Engineer, of The Manor House, Earley,
Reading, Berkshire, and Taipeng Larnt, Penang Straits Settlements, 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 invention relates to levelling and surveying instruments which have diaphragms
with cross lines or wires determining their lines of collination or optical axes.
In order to test the accuracy of the line of collination in such an instrument, I
attach the diaphragm with cross lines or wires and such portions of the instrument as
come between it and the eye of the observer to a piece of tube made to fit the tube in
which the diaphragm is usually fixed, and capable of being easily withdrawn partly,
and inverted as indicated in the accompanying drawing which represents so much of
an instrument of the kind referred to as will serve to explain the application of my
invention, whether in first constructing the instrument or in altering in this manner
an existing instrument. In the drawing, a indicates part of the eye piece, 6 the inner
tube in which the diaphragm is usually fixed, and c the outer tube in which slides. I
fix the diaphragm and its adjuncts in a short piece of tube d (indicated in dotted lines)
which fits in the mouth of the tube b, being preferably held with certain tightness
therein by the spring of the mouth of which is split some distance up for that
purpose. At the mouth of the tube b I form on each side of it a notch or slot e and
on the short tube d I provide two studs f to fit into the slots e. In order to test the
line of collination, it is only necessary to observe first with the tube d in one position
then to partly withdraw the tube until the studs are clear of the slots and having
turned a half round, to push it in, and observe again, so as to ascertain if the inversion
produces a difference of reading.
e,
Having now particularly described and ascertained the nature of my invention and
in what manner the same is to be performed I declare that what I claim is:
.
In a levelling or surveying instrument, fixing the diaphragm and its adjuncts in a
tube capable of being readily inverted, substantially as and for the purpose herein set
forth.
Dated this 4th day of August 1887