IMPROVEMENTS IN SURVEYING IN- STRUMENTS AND IN LEVELLING STAVES CONNECTED THEREWITH
Year: 1877

page_text: LETTERS PATENT to John Benjamin Dancer, of Manchester, in the County of
Lancaster, Optician, for the Invention of "IMPROVEMENTS IN SURVEYING IN-
STRUMENTS AND IN LEVELLING STAVES CONNECTED THEREWITH."
Sealed the au 15
1010
731
PROVISIONAL SPECIFICATION left by the said John Benjamin Dancer at
the Office of the Commissioners of Patents on the 12th December 1877.
John Benjamin DANCER, of Manchester, in the County of Lancaster, Optician.
"IMPROVEMENTS IN SURVEYING INSTRUMENTS, AND IN LEVELLING STAVES CON-
NECTED THEREWITH."
These improvements consist,-
First. In so constructing the eye piecess of the telescopes of levels and theodolites
that they cannot easily fall out and get lost, there being screwed tubes instead of
sliding ones; and this method also facilitates the focussing of the said eye pieces on
the cross line of the diaphragm.
Secondly. The adjusting screws of the diaphragm which carries the cross lines in
this Invention are concealed by a ring or tube, so as to prevent them from being
easily tampered with, instead of being exposed as is usual in such instruments.
Thirdly. The sliding tubes which act on the focus of the telescope in this In-
vention are protected from rain and exposure to weather by means of covering tubes,
which method is not usual in ordinary instruments.
Fourthly. The ends of the screws which belong to those parts of levels and
theodolites known as parallel plates, are made to work on some substance harder
than the gun metal or brass commonly used; in order to prevent the usual wearing
away of the surface of the plates, for this purpose plates of steel, iron, agate, or
various hard substance may be introduced under the ends of the screws.
Price 1

page_text: And, Fifthly. The improvement in levelling staves consists in the employment
of certain rigid material such as papier machè or other japanned or varnished sub-
stance which will resist heat and moisture.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Benjamin Dancer in the Great Seal Patent Office on the 8th
June 1878.
JOHN BENJAMIN DANCER, of Manchester, in the County of Lancaster, Optician.
"IMPROVEMENTS IN SURVEYING INSTRUMENTS, AND IN LEVELLING STAVES CON-
NECTED THEREWITH."
These improvements consist,-
First. In so constructing the eye pieces of the telescopes of levels and theodolites,
that they cannot casily fall out and get lost, there being screwed tubes instead of
sliding ones, and this method also facilitates the focussing of the said cye pieces on
the cross lines of the diaphragm, and in two constructions of levels shewn in the
side view, Fig 1; and the top view, Fig. 2; the screwed eye piece is marked a.
Socondly. The adjusting screws of the diaphragm which carrics the cross lines in
this Invention are concealed by a ring or tube, so as to prevent them from being
easily tampered with, instead of being exposed, as is usual in such instruments, and
in the levol shewn in Fig. 1 there is a ring b which covers the adjusting screws of
the diaphragm, the ring being provided with thumbscrews c, so that it can be
loosened and fastened as required.
Thirdly. The sliding tubes which act on the focus of the telescope are protected
from rain and exposure to weather by means of covering tubes, which method is not
usual in ordinary instruments.
In Fig. 1 the sliding tube, which is at the object glass end of the level, is covered
by a tube d, having an internal thread or screw so fitted to an external screw or
thread e on the main tube f, that it can be placed on and removed as required.
In Fig. 2 the sliding tube is at the eye piece end of the level, and over it I place
a covering tube g, which also covers the adjusting screws of the diaphragm, and is
kept in its place by two thumbscrews h, the tube being well fitted without
screwed threads, so that it can be removed and replaced as required.
Fourthly. The ends of the screws which belong to those parts of levels and theodo-
lites known as parallel plates, are made to work on some substance harder than the
gun metal or brass commonly used in order to prevent the usual wearing away of
the surface of the plates, and for this purpose I embed in the lower parallel plate,
blocks or slabs of hardened steel or other hard substance under the ends of the
screws, and in Fig. 1 these blocks or slabs are shewn at k.
And, Fifthly. The improvement in levelling staves consists in the employment of
certain light materials, such as papier maché or other similar substances which can

page_text: be compressed by hydraulic or mechanical pressure to form light, strong, and rigid
staves which can be varnished or japanned, to resist heat and moisture.
Having now described the nature and particulars of my said Invention, I desiro
it to be understood that I claim the improvements in levels and theodolites used by
surveyors, as herein described and illustrated on the accompanying Sheet of
Drawings, and also the improved system of making levelling staves as described.
In witness whereof, I, the said John Benjamin Dancer have hereunto set my
hand and seal, this Sixth day of June, One thousand eight hundred and
seventy-eight.
Witness,
CHAS. W. COLLINS.
Manchester.
JOHN BENJAMIN DANCER. (L.S.)