A NEW OR IMPROVED EXPANSION BALANCE FOR A CHRONOMETER
Year: 1821

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I JOHN
ROGER ARNOLD, of Chigwell, in the County of Essex, Chronometer and
Timepiece Maker, send greeting.
WHEREAS His most Excellent Majesty King George the Fourth did, by
His Letters Patent under the Great Seal of the United Kingdom of Great
Britain and Ireland, bearing date at Westminster, the Twenty-seventh day
of January, in the first year of His reign, give and grant unto me, the
said John Roger Arnold, my exors, adñors, and assigns, His especial licence,
full power, sole privilege and authority, that I, the said John Roger Arnold,
my exors, admors, and assigns, should and lawfully might, during the term of
years therein mentioned, make, use, exercise, and vend, within England,
Wales, and the Town of Berwick-upon-Tweed, my Invention of "A NEW OR
IMPROVED EXPANSION BALANCE FOR A CHRONOMETER;" in which said Letters
Patent there is contained a proviso that if I, the said John Roger Arnold,
shall not particularly describe and ascertain the nature of my said Invention,
and in what manner the same is to be performed, by an instrument in writing
under my hand and seal, and cause the same to be enrolled in His Majesty's
High Court of Chancery within two calendar months next and immediately
after the date of the said Letters Patent, that then the said Letters Patent,
and all liberties and advantages whatsoever thereby granted, shall utterly
cease, determine, and become void, as in and by the same, relation being
thereunto had, may more fully and at large appear.

page_text: NOW KNOW YE, that in compliance with the said proviso, I, the said
John Roger Arnold, do hereby declare that the nature of my said Invention,
and the manner in which the same is to be performed, are particularly
described, and ascertained in and by the Drawing hereunto annexed, and
the following description thereof (that is to say):-
The expansion of this balance by cold, and its contraction by heat, are pro-
duced by the agency of a single straight expansion piece vibrating about its
own centre. Fig. 2 exhibits a lateral view of the balance. 2-3=6=3=2, is
one piece, the upper part of which from 3 to 3 is of brass; the lower part
from 4 to 4 is of steel. The brass being melted upon the steel, the ends of
the same piece being continued from 3 to 2, are screws, on each of which is
placed a weight 5, which by being screwed nearer to or farther from the the
center 6 will alter the mean time, and occasion it to vibrate faster or slower.
From 4 to 8 are two round arms of steel, rivetted at o, o, into the
shoulders d, d, of the piece 3=6=3, see Fig. 1. These arms are tapped, and
on them are placed the weights a, a, which weights are to regulate the balance
with precision in the different degrees of temperature. Thus let us suppose
that when the thermometer is at temperate, the piece 3-6-3 is straight;
when the heat increases, the brass, expanding more than the steel, will occasion
the piece to become convex on the upper side 3-6-3, and concave on the
lower side 4, 4; by which the weights a, a, will approach the centre, and be
brought nearer to each other, and the balance will be contracted. On the
contrary, as the thermometer falls below temperate, and the cold increases, the
the brass, contracting more than the steel, will cause the upper part 3=6=3, to
become concave, and the lower part 4, 4, convex, by which the weights a, a,
will recede from the center and be thrown farther apart, and the balance will
be expanded. Should the balance go to time in mean temperature, and gain
(for example, thirty seconds per day, in a heat of seventy-six degrees, and lose
in proportion when at the freezing point, the weights a, a, must be screwed in
from 8 towards 4 a certain number of turns, say 6 or 8, as will be determined
by repeated experiments, until a single turn, or the proportional part of a
turn only, will be necessary to make the performance correspond in all the
various degrees. If it should happen that, however far you screw the weights
from 8 towards 4, the balance should still gain in heat, the weights a, a, must
be reduced a certain quantity, for instance, an eighth, or a sixth part. If, on
the contrary, after going to time in mean temperature it should lose in heat
and gain in cold, the weights a, a, must be screwed out from 4 towards 8
(instead of being screwed in from 8 towards 4, as in the first case); and if
when brought to the bottom 8 the balance should still lose more as the heat

page_text: increases, heavier weights must be put on until the necessary adjustments is
found to be the compass of 8 to 4. Fig. 1 exhibits a horizontal view of the
balance. In the middle of the piece are three holes, that in the center is for
the axis to pass through, the others for screws to fix it firmly on the axis.
Altho I have described particular forms and proportions in my Specification,
yet I do not confine myself either to form or proportion where they are variable,
but shall consider any such alteration an infringement on my Patent.
In witness whereof, I, the said John Roger Arnold, have hereunto
set my hand and seal, this Nineteenth day of March, in the year
of our Lord One thousand eight hundred and twenty-one.