AN. INSTRUMENT FOR MEASURING DISTANCES
Year: 1885

page_text: I, HENRY REGINALD ARNULPH MALLOCK, of Brampford Speke in the County'
of Devon, Gentleman do hereby declare the nature of my invention for "AN.
INSTRUMENT FOR MEASURING DISTANCES" to be as follows:-
My, invention relates to an instrument whereby I can, by optical observation,
ascertain the distance of an object. For this purpose, I fix on one end of a rod of
known length, it may be a yard or more, a pair of mirrors set at an angle to
one another of 135° or 45° or nearly so. At the other end of the rod, which is
formed as a stock that can be conveniently held in the hand; I fix another pair of
mirrors at nearly the same inclination to each other as the former pair, but
Imount one of the latter pair on an axis and provide a fine adjusting screw by
which I can vary the inclination of this mirror to the other, this adjusting screw
being furnished with a divided wheel and index by which the divisions can be
read. For measuring a distance, I hold the instrument in such an attitude that
while I look past the pair of mirrors in the stock to a distant object, I see also in
one of them the image of the object reflected from the mirrors at the farther end of
the rod. I then, by means of the adjusting screw, alter the inclination of the
stock mirror until I bring the reflected image into exact coincidence with the
object. I can then read, on the divided wheel, the distance of the object. In order
to provide for greater delicacy of observation, I prefer to make the rod with
additional pieces that can be jointed together so that it can be made of one length.
or double, triple or some other multiple of that length. The reading on the wheel
has then to be multiplied by 2, 3 or the number of jointed pieces used in making
up the rod. I also joint the rod to the stock in such a manner that it can be
turned a little round its own axis by a tangent screw or otherwise, so as to bring
the planes of the one pair of mirrors into proper correspondence with those of the
other pair. The screw wheel may be graduated by equal divisions to be read by a
vernier scale, the instrument being, in that case provided with a table of distances
corresponding to various readings; or the screw wheel may be graduated with
unequal divisions calculated to various distances. The object of employing double
mirrors at both ends of the rod base is to maintain constant the angle of reflection
notwithstanding alteration in the position of either pair of mirrors, a result which
is obtained by the use of double mirrors so long as the inclination of the one to the
other of a pair is not altered.
ر

page_text: I HENRY REGINALD ARNULPH MALLOCK of Brampford Speke, in the County
of Devon Gentleman 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 an instrument whereby I can by optical observation
ascertain the distance of an object. For this purpose I construct an instrument as
I will describe referring to the accompanying drawing shewing a longitudinal
section. I fix on one end of a rod A of known length, it may be a yard or more a
pair of mirrors B and C set at an angle to one another of 135° or 45° or nearly so.
At the other end of the rod A which is formed as a stock D that can be
conveniently held in the hand, I fix another pair of mirrors E and F at nearly the
same inclination to each other as the former pair B and C but I mount one of
the latter pair namely E on an axis and provide a fine adjusting screw G by which
acting on a. spring lever g I can vary the inclination of this mirror E' to .the
other F. The adjusting screw G is furnished with a divided wheel and index H
by which the divisions shewing the extent to which the screw is turned can be
read. For measuring a distance, I hold the instrument by the stock D in such an
attitude that while I look past the pair of, mirrors E and F in the stock D to a
distant object, I see also in one of them E the image of the object reflected from
the mirrors B and C at the farther end of the rod. I then, by means of the
adjusting screw G alter the inclination of the mirror E until I bring the reflected
image into exact visual coincidence with the object. I can then read on the
divided wheel H the distance of the object. In order to provide for greater
delicacy of observation I prefer to make the rod with additional pieces that can be
jointed together as shewn at K, so that it can be made of one length or double,
triple or some other multiple of that length. The reading on the wheel has then to
be multiplied by 2, 3 or the number of jointed pieces used in making up the rod.
I also joint the rod A to the stock in such a manner that it can be turned a little
round its own axis by a tangent screw at L or otherwise, so as to bring the planes
of the one pair of mirrors in to proper correspondence with those of the other pair.
The screw wheel H may be graduated by equal divisions to be read by a vernier
scale, the instrument being in that case provided with a table of distances
corresponding to various readings. Or the screw wheel may be graduated with
unequal divisions calculated to various distances. The object of employing double
mirrors B and C and E and F at both ends of the rod base is to maintain constant
the angle of reflection notwithstanding alteration in the position of either pair of
mirrors, a result- which is obtained by the use of double mirrors so long as the
inclination of the one to the other of a pair is not altered. A telescope M- may be
applied to the stock, and for convenience this may be mounted in such a manner as
to fold back to the stock as indicated at M¹.

page_text: Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:
The construction and use of an instrument for measuring distances, wherein a
pair of mirrors is arranged at each end of a known base and one mirror of one of
these pairs is adjustable by its inclination to the other of the pair by a delicate
screw, the extent of revolution of which gives the measure of the distance of an
object seen past the one pair of mirrors and having its image reflected from the
other pair brought into visual coincidence with the object, substantially as herein
described.