IMPROVEMENTS IN ASTRONOMICAL AND GEO- DETICAL INSTRUMENTS
Year: 1855

page_text: LETTERS PATENT to Charles Piazzi Smyth, of 1, Hillside Crescent, Edin-
burgh, for the Invention of "IMPROVEMENTS IN ASTRONOMICAL AND GEO-
DETICAL INSTRUMENTS."
Sealed the 6th July 1855, and dated the 24th April 1855.
PROVISIONAL SPECIFICATION left by the said Charles Piazzi Smyth at
the Office of the Commissioners of Patents, with his Petition, on the
24th April 1855.
I, CHARLES PIAZZI SMYTH, of 1, Hillside Crescent, Edinburgh, do hereby
declare the nature of the Invention for "IMPROVEMENTS IN ASTRONOMICAL AND
GEODETICAL INSTRUMENTS" to be as follows:-
Part of my improvements consists of what I call spontaneous level points;
they are spirit levels set in collimator tubes, as has been already occasionally
practised, but I arrange them so that the bubble is seen at a constant zenith
distance, though the horizontal position of the whole apparatus be much
disturbed. This novel construction is brought about by making the focal
distance of the collimating lens exactly equal to the radius of curvature of
the level, and by reversing the apparent direction of the motion of the bubble.
Such a level can be used on many occasions where those of the present form
cannot be employed.
Another improvement is applicable where a long bubble in a spirit level is
inconvenient, and where, if it be made short in ordinary temperatures, then in

page_text: extreme ones it may close up and crack the glass tube; and the improvement
consists in having a diaphragm across the inside of the glass tube near its
middle, and a very small tubular passage therein, by which a large bubble of
air may be kept on one side of the diaphragm and a small one on the other;
and should the fluid on the latter side of the diaphragm expand inordinately, it 5
will escape through the passage into the space with the larger bubble, and no
fracture of the glass tube will take place; also by holding one end of the glass
tube up or the other, small particles of air may be shaken from one side of
the diaphragm to the other, and the size of either bubble may be varied at
pleasure.
Another improvement has for its object an adjustable focus collimator. In
existing collimators the optical portion consists of a single lens or a set of
lenses acting as a single acromatic object glass, having one definite focal
distance for parallel rays. The improvement consists in using two or more
lenses, so disposed that by changing the distance between them the focal length
of the combination may be varied at pleasure.
;
Another improvement consists of a free revolving stand, the object of which
is to preserve the horizontality of a platform, large or small, when the base on
which the platform ultimately rests (as, for instance, a ship's deck,) is rolling
and pitching. A well balanced platform is placed in double gymbals, and
connected with it and swinging in the gymbals is a frame containing a heavy
wheel, also balancing in them or altogether balancing in them. When this
wheel is set revolving rapidly, it will preserve its plane and that of the
platform, though the foundations of the gymbals experience great disturbances
of level. And it is the introduction of this heavy revolving wheel into a
frame balancing in the gymbals or points of suspension, for the purpose of
keeping a platform horizontal, which constitutes the peculiarity of this part
of the Invention.
Another improvement applies to single reflection reflecting instruments.
In all the reflecting instruments now used at sea or on land, whether they be
quadrants, sextants, or reflecting circles, one object of the two to be observed
is looked at direct. The improvement consists of causing each object to be
reflected once, in place of one direct view and one double reflection, as
⚫heretofore.
Another improvement is applicable to the standing vernier reflecting circles
It is usual to have the graduated limb in these reflecting circles a fixture and
the vernier moveable, but it is found to be a great advantage to make the
vernier fixed and to make the graduated limb moveable.
Another improvement is in the duplex attachment of tie tube of reflecting

page_text: instruments. Generally such instruments are provided with a telescope tube
and a plain tube, and sometimes one is used and sometimes the other, and in
screwing them in and screwing them out, and sometimes in the accidentally
dropping and losing the said loose tubes, much valuable time is lost. To
avoid these consequences, the telescope and the plain tube are combined
into one piece, which always remains attached to the instrument, and the end
may be accomplished either mechanically or optically. The two tubes may
cross each other, and by pivot motion at their junction one or other may be
brought into position; or the telescope tube may be rendered a plain tube
at pleasure by turning up complimentary glasses before its lenses or by moving.
its lenses.
Another improvement applies to single reflectors altitude azimuth instru-
ment.
This is formed by attaching the single reflections reflecting instrument
previously described, with its plane vertical to an azimuth circle of the ordinary
description.
Another improvement applies to the foot screws of astronomical and geo-
detical instruments. Heretofore they have been loose screws working through
arms connected with the azimuth circle, and the instrument rests on its
stand through the medium of such loose screw, and is not very firm. The
improvement consists in making the foot screws part of the fixed stand,
and they are each supplied with two necks, between which the arms of the
azimuth circle are securely nipped when adjusted to the proper level.
Another improvement applies to micrometer circles. In circular instru-
ments the angle observed is read off by divisions engraved on the limb, but to
read off an angle minutely, or an instrument of small radius, is extremely
difficult. To obviate this, apparatus in the nature of screw micrometer frames
is applied to such circles, whereby minute quantities of motion are magnified
mechanically on the head of the screw by which such motion is effected. For
this purpose the circumferences of the circular instruments are cut into teeth,
wherein works a screw free from end and lateral shake. Large quantities of
motion of the circle are indicated by the number of teeth or of complete
revolutions of the screw, and small quantities of motion or portions of a tooth
or a revolution are shewn much enlarged on the head of the screw.
Another improvement consists of a universal portable reflecting parallactic
tube or equatorial instrument. This tube may be plain or telescopic; it is
made parallactic, or placed parallel to the earth's axis, by being set in a frame
(called the polar frame), which can be raised or depressed in vertical angle and
turned about azimuthally, and made to point to the pole of the sky at the
place. The amount of motion of the polar frame being such as to allow inclina-

page_text: tions from the vertical to the horizontal position, makes it universal or proper
to any place between the poles and the equator, the whole frame and tube
balancing about the motion pivots of the frame. If to one end of such a
tube is attached a reflector moving in a plane parallel to the axis of the tube,
different parts of any meridian may be commanded, and by turning the
tube round its axis different meridians may be obtained.
Another improvement consists of a portable stand, which is constructed of
thin plates in a hollow form, so that it may be filled with water or other
material when great steadiness is required. Such stand when unfilled is light
to carry about, yet offers great firmness when filled.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Charles Piazzi Smyth in the Great Seal Patent Office on the
24th October 1855.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHARLES
PIAZZI SMYTH, of 1, Hillside Crescent, Edinburgh, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-fourth day of April, in the year of our Lord
One thousand eight hundred and fifty-five, in the eighteenth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
Charles Piazzi Smyth, Her special licence that I, the said Charles Piazzi
Smyth, my executors, administrators, and assigns, or such others as I, the
said Charles Piazzi Smyth, my executors, administrators, and assigns, should
at any time .agree with, and no others, from time to time and at all times
thereafter during the term therein expressed, should and lawfully might
make, use, exercise, and vend, within the United Kingdom of Great Britain
and Ireland, the Channel Islands, and Isle of Man, an Invention for "Iм-
PROVEMENTS IN ASTRONOMICAL AND GEODETICAL INSTRUMENTS," upon the condition
(amongst others) that I, the said Charles Piazzi Smyth, by an instrument
in writing under my hand and seal, should particularly describe and ascer-
tain the nature of the said Invention, and in what manner the same was to
be performed, and cause the same to be filed in the Great Seal Patent Office
within six calendar months next and immediately after the date of the said
Letters Patent.
NOW KNOW YE, that I, the said Charles Piazzi Smyth, do hereby
declare the nature of the said Invention, and in what manner the same is

page_text: to be performed, to be particularly described and ascertained in and by the
following statement thereof (that is to say) :-
The first of the said improvements is applicable to spirit levels, & consists
in placing them in a case wherein they are viewed by reflection & through a
collimator lens, whose solar focus is to be made exactly equal in length to the
radius of curvature of the level tube. .
The second of the said improvements is applicable to the regulation of the
size of the air bubble of a spirit level, & consists in introducing into the glass
tube containing the fluid a diaphragm of glass, or of metal perforated by a
small tube in the axis, or nearly so, of the great tube.
The third of the said improvements is applicable to collimators, & consists
in making their object glasses of two or more lenses, capable of having their
distances apart varied at pleasure.
:
The fourth of the said improvements is applicable to preserving a constancy
in the angular position of any small table, shelf, or other such body exposed to
the disturbing motion of a ship at sea; & it consists in having such small
table, shelf, or other such body freely moveable on and balanced about its
point or points of support, & containing within itself one or more wheels, to
which a rapid spinning motion may be given.
The fifth of the said improvements is applicable to reflecting instruments,
as sextants, and consists in causing each of the two objects observed, whenever
an observation is made, to be reflected once on separate reflectors.
The sixth of the said improvements is applicable to the verniers of reflecting
circles, & consists in placing them on the fixed part or the frame of the
instrument, and making the divided limb of the circle the moving part.
The seventh of the said improvements is applicable to the telescope tubes
& plain tubes of reflecting instruments, and consists in making them in a
single block, capable of permanent attachment to the frame of one of the
instruments. This improvement may be carried out either optically or
mechanically. Mechanically, the two tubes may cross & look through each
other, & by pivot motion at their junction one or other may be brought into
position as required. Optically, the telescope tube may be rendered a plain
tube at pleasure by turning up complementary concave glasses before its
lenses, or by turning its lenses out of the optical axis.
The eighth of the said improvements is applicable to altitude and azimuth
instruments, and consists in using a reflecting circle improved, as in the fifth
of the improvements herein-before described, in using such a reflecting circle
for the altitude portion of the altitude and azimuth instrument.
The ninth of the said improvements is applicable to the foot screws of

page_text: astronomical and geodetical instruments, & consists in making such screws
parts of the solid stand on which the instrument rests, the foot of the instru-
ment being caught & fixed on this new plan between two nuts traversing up
& down such fixed screw.
The tenth of the said improvements is applicable to the reading of the
graduation of any astronomical or geodetical instrument, & consists in noting
the number of turns & parts of a turn of an endless screw working in teeth
cut in the limb of such instrument.
The eleventh of the said improvements is applicable to equatorial instru-
ments, & consists in making the telescope tube turn about its own axis, the
said tube resting in a frame which has angular motion in the horizontal &
vertical directions, while a reflector moving on an axis at right angles to the
axis of the telescope is mounted in front of the object glass.
The twelth of the said improvements is applicable to the stands of astro-
nomical & geodetical instruments, and consists in making them of thin metal
plates in a hollow form, so that they may be filled with fluids or comminuted
solids on occasions when great steadiness is required.
In witness whereof, I, the said Charles Piazzi Smyth, have hereunto set
my hand & seal, this Twenty-third day of October, in the year of our
Lord One thousand eight hundred and fifty-five.
CHARLES PIAZZI SMYTH. (L.S.)
Witness,
GEO. HAY,
of 30, Haddington Place, Edinburgh.