A NEW METHOD OF ADJUSTING THE GLASSES OF AND OTHERWISE IMPROVING A CERTAIN INSTRUMENT CALLED HADLEY'S QUADRANT, OTHERWISE HADLEY'S SEXTANT, MUCH USED IN NAVIGATION FOR TAKING THE SUN'S ALTITUDE IN ORDER TO DETERMINE THE LATITUDE, AND FOR MEASURING THE DISTANCE OF THE HEAVENLY BODIES FROM EACH OTHER IN ORDER TO DETERMINE THE LONGITUDE AT SEA
Year: 1772

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, PETER
DOLLOND, of Saint Paul's Church Yard, Optician, send greeting.
WHEREAS His most Excellent Majesty King George the Third did,
by His Letters Patent under the Great Seal of Great Britain, bearing:
date the Twenty-second day of May, in the twelfth year of His reign, give
and grant unto me, the said Peter Dollond, His especial license that I, the
said Peter Dollond, during the term of years therein expressed, should and
lawfully might use,, exercise, and vend, within England, Wales, and Town
of Berwick-upon-Tweed, my Invention of "A NEW METHOD OF ADJUSTING THE
GLASSES OF AND OTHERWISE IMPROVING A CERTAIN INSTRUMENT CALLED HADLEY'S
QUADRANT, OTHERWISE HADLEY'S SEXTANT, MUCH USED IN NAVIGATION FOR TAKING
THE SUN'S ALTITUDE IN ORDER TO DETERMINE THE LATITUDE, AND FOR MEASURING
THE DISTANCE OF THE HEAVENLY BODIES FROM EACH OTHER IN ORDER TO DETERMINE
THE LONGITUDE AT SEA;" in which said Letters Patent there is contained a
provisoe obliging me, the said Peter Dollond, under my hand and seal, to cause
a particular description of the nature of my said Invention, and how the same
is to be performed, to be inrolled in His Majesty's High Court of Chancery

page_text: within four calendar months after the date of the said recited Letters Patent,
as in and by the same (relation being thereunto had) may more fully and
at large appear.
NOW KNOW YE, that in compliance with the said provisoe, I, the said
Peter Dollond, do hereby declare that my said Invention of a New Method of
Adjusting the Glasses of and otherwise Improving a certain Instrument called
Hadley's Quadrant, otherwise Hadley's Sextant, much used in Navigation for
taking the Sun's Altitude in order to determine the Latitude, and for Mea-
suring the Distances of the Heavenly Bodies from each other in order to
determine the Longitude at Sea, is described in the manner following (that is
to say)
-
To adjust the back horizon glass, an index or lever is applied to the brass-
work over which the horizon glass is fixed; means of this index or lever
the back horizon glass is turned on its center and brought into a like position
to that of the fore horizon glass, and by applying a telescope or sight opposite
to the back horizon glass, the said back horizon glass may be adjusted by the
same methods that are commonly used for adjusting the fore horizon glass;
then by turning the index or lever aforesaid, the back horizon glass may be
turned about its center or axis, and the angular motion may be measured by
lines or divisions made on the instrument for that purpose; the back horizon
glass may by this means be brought into the true position required in making
the back observation. To adjust the horizon glasses perpendicular to the
plane of the instrument, a screw is applied to each of the frames that carry
the horizon glasses; these screws pass through the frame of the instrument,
and by turning them with the fingers at the back they are made to alter the
position of the horizon glasses so as to adjust them perpendicular to the
planes of the instrument. To render the motion of the horizon glasses steady
in this adjustment, there is a spring placed underneath the frame of each
horizon glass to act against the screws before mentioned.. The darkening
glasses are placed on that side the horizon glasses which is the furthest from
the observer's eye when he is adjusting the glasses, by that means the object
seen by direct vision may be darkened without darkening the image of the
object seen by reflection.
In witness whereof, I, the said Peter Dollond, have hereunto sett my
hand and seal, the Third day of August, One thousand seven hundred
PETER DOLLOND. (L.s.)

page_text: AND BE IT REMEMBRED, that on the same Third day of August, in
the year above mentioned, the said Peter Dollond came before our said Lord
the King in His Chancery, and acknowledged the Specification of his Inven-
tion aforesaid, and all and every thing therein contained and specified, in form
above written. And also the Specification aforesaid was stampt according to
the tenor of the Statute made in the sixth year of the reign of the late King
and Queen William and Mary of England, and so forth.
Inrolled the Fourth day of August, in the year abovesaid.