IMPROVEMENTS IN OBTAINING A STRAIGHT LINE PARALLEL TO THE AXIS OF THE EARTH, OR IN RENDERING THE AXIS OF A TUBE OR OF A TELFEMODE PARALLEL THERETO
Year: 1852

page_text: LETTERS PATENT to Joseph Hopkins, of Worcester, in the
County of Worcester, Hop Factor, for the Invention of
"IMPROVEMENTS IN OBTAINING A STRAIGHT LINE PARALLEL TO THE
AXIS OF THE EARTH, OR IN RENDERING THE AXIS OF A TUBE OR OF A
TELFEMODE PARALLEL THERETO."
Sealed the 7th June 1853, and dated the 8th December 1852.
PROVISIONAL SPECIFICATION left by the said Joseph Hopkins
at the Office of the Commissioners of Patents, with his Petition,
on the 8th December 1852.
I, JOSEPH HOPKINS, of Worcester, in the County of Worcester,
Hop Factor, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN OBTAINING A STRAIGHT LINE PARALLEL TO THE AXIS OF
THE EARTH, OR IN RENDERING THE AXIS OF A TUBE OR OF A TELESCOPE
PARALLEL THERETO," to be as follows:-
This parallelism is obtained by making one extremity of a line
or axis the centre of a circle, the radius of which is equal to
the tangent of the north polar declination of any close circumpolar

page_text: star; the line being then made perpendicular to the plane of such
circle, and the eye placed at the other extremity of the line, the
circumference of the circle is made to coincide with the circum-
ference of the circle apparently described by the star, by making
corresponding points in those circumferences coincident. Thus at
the
upper transit of the star the highest point of the circle must be
made to coincide with it; at the lower transit the lowest, and vice
versâ, for a telescope carrying an astronomical power. When this
method is used for a telescope (thus converting it into a polar axis,
and affording an easy means of giving an equatorial motion
to another,) its field of view must include exactly double the angle
of the star's north polar declination; and the position of the axis
should be tested by making the telescope revolve round it, when, if
the star continues as it were clinging to the circumference, the
axes of the earth and of the telescope will be truly parallel.
SPECIFICATION in pursuance of the conditions of the Letters
Patent, filed by the said Joseph Hopkins in the Great
Seal Patent Office on the 8th June 1853.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I,
JOSEPH HOPKINS, of Worcester, in the County of Worcester, Hop
Factor, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Eighth day of December, in
the year of our Lord One thousand eight hundred and fifty-two,
in the sixteenth year of Her reign, did, for Herself, Her heirs and
successors, give and grant unto me, the said Joseph Hopkins, Her
special licence that I, the said Joseph Hopkins, my executors, admi-
nistrators, and assigns, or such others as I, the said Joseph Hopkins,
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

page_text: "
and Ireland, the Channel Islands, and Isle of Man, an Invention for
"IMPROVEMENTS IN OBTAINING A STRAIGHT LINE PARALLEL TO THE AXIS OF
THE EARTH, OR IN RENDERING THE AXIS OF A TUBE OR OF A TELESCOPE
PARALLEL THERETO
upon the condition (amongst others) that I, the
said Joseph Hopkins, by an instrument in writing under my hand
and seal, should particularly describe and ascertain 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 Joseph Hopkins, do hereby
declare the nature of my said Invention, and in what manner the
same is to be performed, to be particularly described and ascer-
tained in and by the following statement thereof, reference being
had to the Drawings hereunto annexed, that is to say:
The
My Invention consists in certain mechanical arrangements
whereby I am enabled to obtain a straight line, which may
be either an extended wire, the axis of a plain tube, or of a
telescope parallel to the axis of the earth, which may be applied to
the construction of sun dials, by which minute portions of time
may be ascertained, or to the production of equatorial motion in
a telescope. This parallelism is obtained by making one extremity
of a line or axis the centre of a circle, the radius of which (the
length of the line being taken as the unit) is equal to the tangent
of the north polar distance of any close circumpolar star.
line being then made perpendicular to the plane of such circle, and
the eye placed at the other extremity of the line, the circumference
of the circle is made to coincide with the circumference of the circle
apparently described by the star, by making corresponding points
on those circumferences coincident; thus at the upper transit of the
star the highest point of the circle must be made to coincide with
it; at the lower transit the lowest, and vice versa for a telescope
carrying an astronomical power. When this method is used for
a telescope (thus converting it into a polar axis, and affording
an easy means of giving equatorial motion to another,) its field of

page_text: view must include exactly double the angle of the star's north
polar distance, and the position of the axis should be tested by
making the telescope revolve round its axis; when, if the star
continues as it were clinging to the same point of the circumference,
the axes of the earth and of the telescope will be truly parallel, and
this without the usual preliminary requirements of a knowledge of
the latitude and directions of the meridian, and without the
preparatory aid of levels or divided circles. Figure 1, of the
Drawings hereunto annexed represents the method which I propose
to adopt for giving equatorial motion to a telescope. A, A,
is a common tripod telescope-stand, upon the top of which is
mounted a vertical projecting piece or pin, shewn in dotted lines,
which forms the axis around which a socket B, is free to revolve
when required in a horizontal direction; C, is a brass tube, which is
attached to the socket B, by a joint a, which allows of a vertical
motion being imparted to the tube C. The tube C, and socket B, may
be clamped in any required position by the pinching screws b, and c,
so as to render them firm when once set, and not liable to derange-
ment. The tube C, is made of five inches in length, and has
inserted into one end of it an eye piece, in the centre of which is
drilled a hole of about 16th of an inch in diameter; and at the other
end of the tube is fixed an object cover, with a central circular
aperture of about one quarter of an inch in diameter, so that the
eye of the observer, being directed through the eye piece, will take
in a field of view, the circumference of which will be about
equal to that of the circle which Polaris apparently describes round
the true polar point; so that, if before fixing the position of
the instrument by the pinching screws b, and c, through the
horizontal and vertical motions, these circumferences be made
to coincide, their centres will also be the same, and the axis of the
tube will be parallel to the axis of the earth. This coincidence may
be nearly enough obtained where a plain tube only is used by
viewing the polar star on that part of the circumference of the
circular diaphragm nearest to the constellation Cassiopeia; but where
greater accuracy is required, I prefer using a telescope the axis of

page_text: which is made parallel to the axis of the earth in the following
manner:-On the outside of the tube of the telescope are fitted two
circular metal rings e, and f, Figure 1, which are carefully ground
into corresponding collars in the metal tube C, the axis of the
telescope exactly coinciding with the common axis of the collars
and tube C; and the centre of its diaphragm is made to coincide
with this axial line, the diameter of the diaphragm being such as to
give a field of view to the telescope of 2° 57', or double the north
polar distance of Polaris. H, is a brass sector, which is separately
shewn in full size in Figure 2, which is capable of being moved
round the upper portion of the brass tube C, being provided with a
collar g. This sector is placed at right angles to the tube, and has
engraved upon it an index line; it is also provided with two small
perforations, which correspond to the relative positions of the stars
E, and Z, Ursa Majoris; so that when these perforations are directed
to the above stars, and are seen by the observer, the eye also taking in
the field of view of the telescope, the position to which Polaris must
be brought on the circumference is indicated by the index line. In
order to test the accuracy of the parallel line thus found, the
telescope is turned one complete revolution in its sockets; and
should Polaris still continue to be seen on the same point of the
circumference of the diaphragm of the telescope, it will be known
that the line is correct, and that the axis of the telescope exactly
corresponds with the axis of the earth. The line of parallelism
being thus obtained, the small telescope and sector are removed
from the tube C, and I insert the spindle or axis I, of a larger tele-
scope for making any requisite astronomical observation: this
arrangement is separately represented in Figure 3, together with
the apparatus which I propose to adopt, giving equatorial motion
to the telescope; and also, should the instrument be directed to any
particular star, and motion imparted to it from east to west, the
object will be kept in the field of view. Upon the end of the axis
I, is placed a double-grooved pulley K, kept in its place by a circular
nut L, upon the screwed portion of the axis; the pulley is connected
to the axis I, by incans of a feather and groove; so that, as it is

page_text: caused to revolve in the manner hereinafter explained, it shall
impart a like rotary motion to the telescope M. The telescope M,
is attached to the axis I, by the circular clamps h, h, and joint e,
which admits of vertical motion being given to the telescope. The
upper groove of the pulley K, is made exactly twenty-four inches
in circumference, while that of the lower groove is nearly equal to
twenty-five inches, the former bearing to the latter the proportion
of the sidereal to the mean lunar day. In making a sidereal obser-
vation, the cord N, is passed over the upper groove, as indicated
in the Figure, the cord being kept in its place by the clamp O;
one end of the cord N, is attached to a weight P, which is sunk
into the centre of a circular tray Q, which floats upon water placed
in the receiver R; S, is a glass syphon, which is attached to one
side of the floating trough, one leg of which dips into the water in
the reservoir, and the bore of the syphon is made of such a size so
as, with the rack and pinion adjustment, to run the water off at a
speed which shall exactly correspond with the required speed of the
revolution of the pulleys, so as to adapt the revolution of the tele-
scope to the motion of the star. T, is a small weight attached to
the other end of the cord, so as to give to it the requisite degree of
tension; the leg S', of the syphon is passed through collars m, m,
attached to a rack U, which can be raised or lowered by means of a
pinion on the spindle of the thumb screw u, so as to adjust the
length of the syphon to run the water off at a speed equal to one
gallon in one mean solar hour; W, is a cock, which is placed at the
bottom of the reservoir R, and is capable of being turned, by means
of the rod X, terminating in the milled head Y, so as to open the
outflow of the water, should the star be at all in advance of the
telescope, which usually happens at the commencement of the ob-
servation: the circular tray Q, is thus caused to fall more rapidly,
and a quicker speed is imparted to the revolution of the telescope,
until the object shall coincide with the centre or axial line of the
telescope, when the extra flow of water is stopped by shutting off
the cock w, and the water is caused to flow through the syphon
only. Should it be desired to follow the motion of the moon, the

page_text: cord must be removed to the lower groove of the pulley K; this
pulley K, represents the right ascension circle.
And having now described the nature of my said Invention, and
the manner in which the same is to be performed, I declare that I
claim the obtaining a straight line, which may be either an extended
wire, the axis of a tube or of a telescope, parallel to the axis of the
earth, by means of the mechanical arrangements and in the manner
hereinbefore described and exemplified in Figures 1, and 2, of the
Drawings hereunto annexed.
In witness whereof, I, the said Joseph Hopkins, have hereunto
set my hand and seal, this Eighth day of June, One thou-
sand eight hundred and fifty-three.