IMPROVEMENTS IN CHRONOMETERS AND OTHER TIME-KEEPERS
Year: 1856

page_text: LETTERS PATENT to John Gottlieb Ulrich, of 63, Mark Lane, in the City
of London, for the Invention of "IMPROVEMENTS IN CHRONOMETERS AND
OTHER TIME-KEEPERS."
Sealed the 11th July 1856, and dated the 14th January 1856.
PROVISIONAL SPECIFICATION left by the said John Gottleib Ulrich at
the Office of the Commissioners of Patents, with his Petition, on the 14th
January 1856.
I, JOHN GOTTLIEB ULRICH, of 68, Mark Lane, in the City of London, do
hereby declare the nature of the Invention for "IMPROVEMENTS IN CHRONO-
METERS AND OTHER TIME-KEEPERS," to be as follows:-
My improvements consist, first, in certain improvements in what are
commonly compensation curbs, and other contrivances, for effecting a com-
pensation for change of temperature.
Secondly, in certain contrivances for facilitating the equalizing of the
vibrations of the balance, or rendering the balance spring isochronous,
commonly known by the term isochronism, by making the long vibrations to
be performed in the same space of time as the short ones.
The above improvements are applicable to clocks and regulators, as well as
marine and pocket chronometers.

page_text: Thirdly, in improvements in the compensation balance of the ordinary
construction, for making it useful for every change of temperature from zero
to 130° of Fahrenheit.
Fourthly, in certain contrivances for suspending the chronometers in
gymbals, upon double universal joints (made with caps and points or pivots) 5
attached to supports in the box.
Fifthly, in improved bolts or stays for securing the chronometer when being
carried to or from the ship, or elsewhere.
Sixthly, in certain contrivances for preventing the detent of the.usual
detached escapement from the concussion which takes place in coming to its
banking screw.
Seventhly, in certain improvements upon the lever escapement for reducing
the amount of friction in unlocking and receiving of impulse, and in the guard
for the prevention of tripping.
Eighthly, in certain improvements upon escapements, commonly known by 1
the name of Remantoire escapements, chiefly to clocks and regulators.
Ninethly, in certain improvements upon the compensation pendulum, and
other kinds of compensations for clocks and regulators, instead of a compen--
sation pendulum.
The first part of my Invention is shown at Figure 1, which is a view of the s
first portion of the balance spring, as fixed in the stud shown at A. To com-
pensate for the variation of tension that takes place in the tension of the
balance spring upon a change of temperature, a tube of brass B (or other
metal of large expanding properties) is placed upon a moveable plate of steel
C, (iron, platina, or other metal, of little expanding properties) concentric with
the balance axis, similar to the index of a common watch, and as upon an
increase of temperature, the end of the brass tube at c approaches the inner
part of the balance spring, it contracts its action, and supplies the deficiency of
tension that the heat had produced; and upon a decrease of temperature, the
reverse. As in practice it is not convenient to have a tube of sufficient length
to obtain enough compensation, recourse should be had to supply that incon-
venience, by using several tubes of brass, with intermediate ones of steel, iron,
or platina, alternately enclosed in each other, placed upon the moveable plate C.
A combination of several tubes will also effect a very good compensation by
being connected with the end of one of two springs on the balance axis, or it
will do if it is only connected with the end of one of the two springs, providing
the expanding tubes are of sufficient length to compensate enough.
Secondly, Figure 1 also represents by a curve line D (representing a portion
of an internal epycycloid) for allowing the balance spring to lean against as it
'

page_text: opens, to enable it to exert greater power upon the balance as the balance
increases in its vibrations, from whatever cause it may happen. This epy-
cycloidal piece is to be screwed as close as possible to the balance spring at the
stud and reduced in thickness at the root to render it flexible. It is guarded
at its extremity by a small adjusting screw F, fixed in a stud on the balance
cock.
Thirdly, Figure 2 shows an improvement upon the chronometer balance of
the ordinary construction. A represents the ordinary construction of compen-
sation balance; B, B, the improvement, which are portions of a circle of two
metals united, silver or brass, and aluminium or palladium; in preference to
steel, or any lighter metal than platina which is not subject to magnetism,
placed in a vertical position on the laminae of the balance, as shown at C. Each
circle C contains a screw of platina (which being the heaviest metal is the best.)
Upon an increase of temperature this said screw has two motions, one towards
the centro of the balance axis, and the other towards the end of the laminae
on which it is fixed, by which a greater leverage is obtained, and thus causes
a greater quantity of weight to approach the centre of the balance, for a given
change of temperature to heat, than what will recedo from the centre for a
corresponding change of temperature for cold. This part of the Invention
admits of a variety of modifications; the above is, however, I believe, the
most convenient form in which this my new system of compensation can be
carried out.
The fourth part of my Invention consists in certain contrivances for sus-
pending chronometers in gymbals, upon double universal joints. A, Figures 3
and 4, represent a frame to be placed inside of the wooden box upon the
pivots B, B, supported by a spring, not shown. C represents a ring, in which
the chronometer with its brass box is placed. The ring C is supported in the
cups of the loops E, E, upon its points D, D, which are supported on the
studs F, F, of the framo A.
Fifthly, the bolt or stay for securing the chronometer, while being carried to
to or from the ship, is effected by making two notches for the bolt to be
alternately placed in, similar to what is commonly known as the bayonet lock,
and to be preserved from getting out of this notch by a spring which is
continually pressing 'against it. A, Figure 5, is a brass frame screwed into
one corner of the chronometer box; B is the head of a bolt, which upon being
withdrawn from the notch, and pressed forward into the notch C, secures tho
chronometer.
Sixthly, Figure 6 represents certain contrivances for preventing the detent
of the usual detached escapement from the concussion which takes place in

page_text: coming to its banking: A represents the usual kind of tooth of the ordinary
kind of chronometer escape wheel; in which it is well understood tliat as soon
as the detent (which stops its rotation) is lifted out, it proceeds forward; and
the detent drops in again to micet the succeeding tooth atitl stop the whicel; but
in dropping from the lifting pallet on the, balance axis, it invariably falls with
such force against its banking screw that it frequently beats a hole into it.
Figure 7 represents another kind of tooth, whereby the detent as soon as it
is liberated from the front surface of the tootli, it is carried up an inclined
plane, where it is left by the lifting pallet on the balance axis, and as the
wheel proceeds, it slips down gradually at the back of the tooth, until it comes
to rest against its banking. If it should be thought too much trouble to cut a
wheel with such teeth, the same principle can be equally as effectively carried
out by making the detent pallet of the same shape as the tooth.
Seventhly, Figure 8 represents certain improvements upon the lever escape-
ment. A represents the large roller on the balance axis; B, 'n ruby pallet
inserted in the arm on the balance axis, for the reception of an inpulse, which
it receives alternately direct from the teeth of the escape wheel, in a similar
manner nearly to the well-known pin-wheel escapement of a clock. D, D, are
a pair of detent pallets, for acting alternately in the teeth of the escape wheel:
The principal part of the improvements consist in making a separate roller on
the balance axis, of the same diameter as the unlocking pins, and of having
those pins at such a distance from cach other, that the unlocking may take
place as near as possible to the line of centres between the balance axis and
the detent pivots.
Eighthly, I will now describe iny improvements on the Romontoire escape-
ments. Figure 9 represents an escape wheel A, which raises alternately the
levers B and C that carry the weights E and F, which gives impulse to the
pendulum G at the extremity of each vibration. II is a lever, containing a pair
of pallets I, I, that stops the rotation of the fly connected with the escape
wheel, and which is alternately liberated by means of one of the arms 1, 2, of
the levers B and C raising one of the weights E or F from the pallet lever
J, J, and thereby allowing the remaining weight to alter the position of the
pallets I, I, which enables the fly to move half round, and the escape wheel
then raises the other weight to give the succeeding impulse to the pendulum;
K, K, are two detents for the prevention of tripping, and are drawn away
from the pallets I, I, by an arm L, L, on the levers B and C, just before the
pendulum is going to receive impulse. Figure 10 shows another escapement,
in which the impulse is given to the pendulum as near as possible when it
is passing the quiescent point, (which is the leading feature thereof). The

page_text: rotation of the fly is stopped by an arın alternately resting on one of the pair
of pallets, shewn at O, O, and unlocked by a pin at the bottom of the pen-
dulum entering into the fork of a lever, similar to the well-known lever of a
common watch; and directly that one of the ruby pallets at the other end
of the lever is removed from the fly, one of the impulse levers gives impulso
to the pendulum, as seen at A, which will make it vibrator nearly one inch.
Upon the return of the pendulum the ruby pallet B comes within the orbit
of the impelling lever C, and immediately afterwards, through the ruby pin at
the centre of the pendulum entering the fork, liberates the fly, which by
proceeding forward, allows the tooth of the escape wheel to pass beyond the
ruby pallet D, and causes the impelling lever C to give the impulse through
its weight E.
Ninthly, A, Figure 11, represents a brass frame for the suspension spring
of a pendulum to pass (moderately freely) through; and supported by the lever
B, which is acted upon by the levers C, C, C, in connection with the tube or
tubes D, the lower end of which is fixed with the lever to an iron plate. The
compensation being effected by the tubes being made of brass, or a metal
expanding more than iron, and by acting upon the levers, causes the pendulum
to be raised to a greater height for any given change of temperature to heat,
than what it would be lowered for the same quantity to cold. The spring E
must be nearly strong enough to sustain the pendulum.
The inaccurate performance of the best astronomical time-keepers that are
made is occasioned principally though a change of temperature, and to remedy
which, among the various ingenious devices that have been produced, the
one most generally adopted in the English observatories is the mercurial
pendulum.) For a pendulum that rests upon a knife edge, it is only necessary
to apply a column of mercury of a sufficient height to rise or fall in such
proportion as shall be adequate to the lengthening or shortening of the rod, for
the purpose of preserving the centre of gravity at the same distance from the
point of suspension, under every variation of temperature; but in a pendulum
that is suspended by a spring (which is by far the best method, and the one
most generally adopted,) there is something beyond the length of the suspension
spring and rod to compensate; there is the variation of tension in the suspen-.
sion spring to compensate for, and which in the usual construction of pendulum
cannot be accomplished without the introduction of an evil, viz., (an excess of
compensation), which is equally as great as the one sought to be remedied,
and in extreme cold, greater; for after the length of the suspension spring and
rod is compensented for, the smallest additional quantity of mercury is a source
of error, and that quantity which is absolutely necessary to compensate for the

page_text: variation of tension in the suspension spring is the cause of all the mischief,
which is to be proved from the well-known law upon which the theory of the
pendulum is founded, and its length ascertained, and from which it is known
to be an indisputable fact that the raising the ball (or column of mercury) of a
pendulum one inch, (or any given quantity), however small, will not make so
much alteration in the times of its vibration, as lowering it the same quantity;
hence arises the expediency of making the centre of gravity rise in an
accelerated proportion upon an increase of temperature, and to descend in a
diminished or retarded proportion upon a decrease of temperature.
To effect this, a cone or a solid (generated by the revolution of a geometrical
curve) attached to a silver tube is immersed in mercury. By an increase of
temperature the silver tube expands downwards, and being fixed at one end,
the solid is immersed to a greater depth in the mercury, which, consequently,
rises in the glass cylinder in a ratio dependant on the form of the solid.
Figure 12 shows the arrangements I employ to produce this effect. A repre-
sents the stirrup, with a portion of the rod and the regulating nut and screw;
B, the glass cylinder to contain the mercury; C, the secondary compensation
tube or tubes, to which are attached the inverted cone D; D, the inverted conc,
or geometrical curve; E, the permanent clip which holds the tube to the stirrup;
F, F, the screws which hold the above clip to the tube; G, G, the screws which
hold the above clip to the stirrup; H, the temporary clip for holding the tube
to the stirrup, while the permanent clip is shifted up or down to obtain the
requisite length of tube for the secondary compensation; I, a nut with a nurled
head and engraved divisions of 100, placed upon a tube (attached to the clip)
upon which tube is cut a screw of fifty threads to the inch. By means of this
nut the permanent clip is to be adjusted, and after any alteration is made, the
said nut, as now shown in the Drawing, is to be removed from contact with
the permanent clip; and the screws K, K, which hold the temporary clip II
to the stirrup, must be slackened, to allow a free action of the tube C upon a
ohange of temperature, at the same time keeping the clip tight upon the tube
C; L, a steel spring at the bottom of the glass cylinder, for the extremity of
the cone D to rest in, to prevent Interal motion; M, the line, shewing the
height of mercury at mean temperature.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said John Gottlieb Ulrich in the Great Seal Patent Office on
the 12th July 1856.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
GOTTLIEB ULRICH, of 63, Mark Lane, in the City of London, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Fourteenth day of January, in the year of our Lord
One thousand eight hundred and fifty-six, in the nineteenth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said John Gottlieb Ulrich, Her special licence that I, the said John
Gottlieb Ulrich, my executors, administrators, and assigns, or such others as
I, the said John Gottlieb Ulrich, 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 "IM-
PROVEMENTS IN CHRONOMETERS AND OTHER TIME-KEEPERS, upon the condition
(amongst others) that I, the said John Gottlieb Ulrich, my executors or
administrators, by an instrument in writing under my, or their, or one of
their hands and seals, 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 tho said Letters Patent.
NOW KNOW YE, that I, the said John Gottlieb Ulrich, do hereby
declare the nature of the said Invention, and in what manner the same is to
be performed, to be particularly described and ascertained in and by the fol-
lowing statement thereof, that is to say :-
My improvements consist, first, in certain improvements in what are com-
monly known as compensation curbs, and other contrivances, for effecting a
compensation for change of temperature.
Secondly, in certain contrivances for facilitating the equalizing of the vibra-
tions of the balance, or rendering the balance spring isochronous, commonly
known by the term isochronism, by making the long vibrations to be performed
in the same space of time as the short ones.
The above improvements are applicable to clocks and regulators as well as
marine and pocket chronometers.
Thirdly, in improvements in the compensation balance of the ordinary
construction, for making it useful for every change of temperature from zero

page_text: '
to 180° of Fahrenheit, and destroying its tendency to being affected by ter-
restial magnetism, or local attraction; on board of iron ships in particular.
Fourthly, in certain contrivances for suspending the chronometers in
gymbals, upon double universal joints (made with caps and points or pivots)
attached to supports in the box.
Fifthly, in improved bolts or stays for securing the chronometer when being
carried to or from the ship, or elsewhere.
Sixthly, in certain contrivances for preventing the detent of the usual
detached escapement from the concussion which takes place in coming to its
banking screw.
Seventhly, in certain improvements upon the lever escapement for reducing
the amount of friction in unlocking and receiving of impulse, and in the guard
for the prevention of tripping.
Eighthly, in certain improvements upon escapements, commonly known by
tho name of Remontoire escapements, chiefly to clocks and regulators.
Ninthly, in certain improvements upon the compensation pendulum, and
other kinds of compensation for clocks and regulators, instead of a compen-
sation pendulum.
The first part of my Invention is shown at Figure 1, which is a view of the
first portion of the balance spring as fixed in the stud, shewn at A. To com-
pensate for the variation of tension that takes place in the tension of the
balance spring upon a change of temperature, a tube of brass B (or other
metal of large expanding properties) is placed upon a moveable plate of steel
C, (iron, platina, or other metal, of little expanding properties) concentric with
the balance axis, similar to the index of a common watch, and as upon an
increase of temperature, the end of the brass tube at c approaches the inner
part of the balance spring, it contracts its action, and supplies the deficiency of
tension that the heat had produced; and upon a decrease of temperature, the
foversc. As in practice it is not convenient to have a tube of sufficient length
to obtain enough compensation, recourse should bo had to supply that in-
convenience by using several tubes of brass, with intermediate ones of steel,
iron, or platina, alternately inclosed in each other, placed upon the moveable
plate C. A combination of several tubes will also effect a very good com-
pensation by being connected with the outer ends of two springs on the
balance axis, or it will do if it is only connected with the outer end of one of
the two springs, providing the expanding tubes are of sufficient length to com-
pensate enough. Heat causing the springs to be coiled up, and cold causing
them to be uncoiled, the amount depending upon the length of the tubes.
Secondly, Figure 1 also represents by a curved line D (representing a

page_text: portion of an internal epycycloid) for allowing the balance spring to lean
against as it opens, to enable it to exert greater power upon the balance as
the balance increases in its vibrations, from whatever cause it may happen.
This epycycloidal piece is to be screwed as close as possible to the balance
spring at the stud, and reduced in thickness at the root to render it flexible.
It is guarded at its extremity by a small adjusting screw F, fixed in a stud on
the balance cock; or the same object may be effected by the introduction of
two or three screws being placed in a stud on the cock opposite to the first
half turn of the balance spring, allowing the screw farthest from the pendulum
stud to be at such a distance from the spring as only to touch it when the
balance is turned half round, and the screw nearest to the stud to touch it
when the balance is turned one quarter round. This I have found to give
complete controul over the long and short vibrations.
Thirdly, Figure 2 shows an improvement upon the chronometer balance of
the ordinary construction. A represents the ordinary construction of com-
pensation balance; D is a thin armature of iron connected to the laminae at
E, F, by screws, to connect the magnetic current, the same as is done by the
armature of a common horse-shoe magnet. The above has reference to the cor-
rection or improving the state of old chronometers; but in the manufacture
of new ones, I fix a compensated laminae or hoop to a metal bar (where
extra expence is not an object, I use the new metal, aluminium). For cheaper
work, I use a disc of talc, with the edge secured by a frame of brass. After
mounting the hoop, I cut it open and apply the extra compensating circles.
The improvement, which are portions of a circle of two metals united,
silver or brass, and aluminium or palladium, in preference to steel, or any
lighter metal than platina which is not subject to magnetism, placed in a
vertical position on the lamina of the balance, as shown at C. Each circle
C contains a screw of platina (which being the heaviest metal is the best).
Upon an increase of temperature this said screw has two motions, one towards
the centre of the balance axis, and the other towards the end of the lamina
on which it is fixed, by which a greater leverage is obtained, and thus causes
a greater quantity of weight to approach the centre of the balance of a given
change of temperature to heat, than what will recede from the centre for
a corresponding change of temperature for cold. This part of the Invention
admits of a variety of modifications. The above is, however, I believe, the
most convenient form in which this my new system of compensation can be
carried out. I, however, subjoin another with aluminium tubes, which can be
mounted on a bar of gold or platina, but I prefer a disc of tale, on account of
its being much lighter.

page_text: The fourth part of my Invention consists in certain contrivances for sus
pending chronometers in gymbals, upon double universal joints. A, Figures 3
and 4, represent a frame to be placed inside of the wooden box upon the
pivots B, B, supported by a spring, not shewn. C represents a ring, in which
the chronometer with its brass box is placed. The ring C is supported in the
cups of the loops E, E, upon its points D, D, which are supported on the
studs F, F, of the frame A. This contrivance prevents the chronometer from
being affected by the tremor of steam ships, or being injured by the lateral
motion or concussion to which they are too often subjected to.
Fifthly, the bolt or stay for securing the chronometer, while being carried
to or from the ship, is effected by making two notches for the bolt to be
alternately placed in, similar to what is commonly known as the bayonet lock,
and to be preserved from getting out of this notch by a spring, which is
continually pressing against it. A, Figure 5, is a brass frame screwed into
one corner of the chronometer box. B is the head of a bolt, which upon
being withdrawn from the notch, and pressed forward into the notch C,
secures the chronometer.
Sixthly, Figure 6 represents certain contrivances for preventing the detent
of the of the usual detached escapement from the concussion which takes
place in coming to its banking. A represents the usual kind of tooth of the
ordinary kind of chronometer escape wheel, in which it is well understood
that as soon as the detent (which stops its rotation) is lifted out, it proceeds
forward, and the detent drops in again to meet the succeeding tooth, and stop
the wheel; but in dropping from the lifting pallet on the balance axis, it
invariably falls with such force against its banking screw that it frequently
beats a hole into it.
Figure 7 represents another kind of tooth whereby the detent, as soon as it
is liberated from the front surface of the tooth, it is carried up an inclined
plane, where it is left by the lifting pallet on the balance axis, and as tho
wheel proceeds, it slips down gradually at the back of the tooth until it comes
to rest against its banking. If it should be thought too much trouble to cut
a wheel with such teeth, the same principle can be equally as effectively.
carried out by making the detent pallet of the same shape as the tooth.
Seventhly, Figure 8 represents certain improvements upon the lever escape-
ment. A represents the large roller on the balance axis; B, a ruby pallet,
inserted in the armi on the balance axis for the reception of impulse, which it
receives alternately direct from the teeth of the escape wheel, in a similar
manner nearly to the well-known pin-wheel escapement of a clock; D, D, arc
a pair of detent pallets, for acting alternately in the teeth of the escape wheel.

page_text: The principal part of the improvements consists in making a separate roller on
the balance axis, of the same diameter as the unlocking pins, and of having
those pins at such a distance from each other, that the unlocking may take
place as near as possible to the line of centres between the balance axis and
the detent pivots.
Eighthly, I will now describe my improvements on the Remontoire escape-
ments. Figure 9 represents an escape wheel A, which raises alternately the
levers B and C that carry the weights E and F, which gives impulse to the
pendulum G at the extremity of each vibration; H is a lever containing a pair
of pallets I, I, that stops the rotation of the fly connected with the escape
wheel, and which is alternately liberated by means of one of the arms 1, 2, of the
levers B and C, raising one of the weights E or F from the pallet lever J, J,
and thereby allowing the remaining weight to alter the position of the pallets
I, I, which enables the fly to move half round, and the escape wheel then
raises the other weight to give the succeeding impulse to the pendulum; K, K,
are two detents, for the prevention of tripping, and are drawn away from the
pallets I, I, by an arm L, L, on the levers B and C, just before the pendulum
is going to receive impulse. Figure 10 shows another escapement, in which
the impulse is given to the pendulum as near as possible when it is passing
the quiescent point, (which is the leading feature thereof). The rotation
of the fly is stopped by an arm, alternately resting on one of the pair of
pallets shown at 0, 0, and unlocked by a pin at the bottom of the pendulum
entering into the fork of a lever, similar to the well-known lever of a common
watch, and directly that one of the ruby pallets at the other end of the lever is
removed from the fly, one of the impulse levers gives impulse to the pen-
dulum, as seen at A, which will make it vibrate nearly one inch (if the escape-
ment is placed at the bottom of the pendulum). Upon the return of the
pendulum, the ruby pallet B comes within the orbit of the impelling lever C,
and immediately afterwards, through the ruby pin at the centre of the pen-
dulum entering the fork, liberates the fly, which, by proceeding forward, allows
the tooth of the escape wheel to pass beyond the ruby pallet D, and causes the
impelling lever C to give the impulse through its weight E. The guard pin,
for the prevention of tripping, or allowing the lever to get on the wrong side, is
to be placed in the lever at same part of the fork as is usually done in the
lever of the ordinary watch escapement.
Ninthly, A, Figure 11, represents a brass frame, for the suspension spring
of a pendulum to pass (moderately freely) through, and supported by the lever
B. which is acted upon by the levers C, C, C, in connection with the tube or
tubes D, the lower end of which is fixed with the lever to an iron plate, the

page_text: compensation being effected by the tubes being made of brass, or a metal
expanding more than iron, and, by acting upon the levers, causes the pendulum
to be raised to a greater height for any given change of temperature to heat
than what it would be lowered for the same quantity to cold. The spring E
must be nearly strong enough to sustain the pendulum.
The inaccurate performance of the best astronomical time-keepers that are
made is occasioned principally through a change of temperature, and to remedy
which, among the various ingenious devices that have been produced, the one
most generally adopted in the English observatories is the mercurial pendulum.
For a pendulum that rests upon a knife edge, it is only necessary to apply a
column of mercury of sufficient height to rise or fall in such proportion as
shall be adequate to the lengthening or shortening of the rod, for the pur-
pose of preserving the centre of gravity at the same distance from the point
of suspension under every variation of temperature; but in a pendulum that
is suspended by a spring (which is by far the best method, and the one
most generally adopted,) there is something beyond the length of the sus-
pension spring and rod to compensate; there is the variation of tension in
the suspension spring to compensate for, and which, in the usual construction
of pendulum, cannot be accomplished without the introduction of an ovil, vide-
licit (an excess of compensation), which is cqually as great as the one sought
to be remedied, and in extreme cold, greater; for after the length of the
suspension spring and rod is compensated for, the smallest additional quantity
of mercury is a source of error, and that quantity which is absolutely necessary
to compensate for the variation of tension in the suspension spring is the cause
of all the mischief, which is to be proved from the well-known law upon which
the theory of the pendulum is founded, and its length ascertained, and from
which it is known to be an indisputable fact, that the raising the ball (or
column of mercury) of a pendulum one inch (or any given quantity) however
small, will not make so much alteration in the times of its vibration as lower-
ing it the same quantity; henco arises the expediency of making the centre of
gravity rise in an accelerated proportion upon an increase of temperature, and
to descend in a diminished or retarded proportion upon a decrease of tem-
perature. To effect this, a cone or a solid (generated by the revolution of a
geometrical curve) attached to a silver tube is immersed in mercury. By an
increase of temperature, the silver tube expands downwards, and being fixed
at one end, the solid is immersed to a greater depth in the mercury, which
consequently rises in the glass cylinder in a ratio dependant on the form of
the solid.
Figure 12 shows the arrangements I employ to produce this effect. A

page_text: represents the stirrup, with a portion of the rod and the regulating nut and
screw; B, the glass cylinder, to contain the mercury; C, the secondary com-
pensation tube or tubes, to which are attached the inverted cone D; D, the
inverted coné, or geometrical curve; E, the permanent clip, which holds the
tube to the stirrup; F, F, the screws, which hold the above clip to the tube;
G, G, the screws which hold the above clip to the stirrup; H, the temporary
clip, for holding the tube to the stirrup while the permanent clip is shifted
up or down to obtain the requisite length of tube for the secondary com-
pensation; I, a nut, with a milled head and engraved divisions of 100,
placed upon a tube (attached to the clip), upon which tube is cut a screw of
fifty threads to the inch. By means of this nut the permanent clip is to be
adjusted, and after any alteration is made, the said nut, as shewn on the Draw-
ing, is to be removed from contact with the permanent clip, and the screws
K, K, which hold the temporary clip H to the stirrup, must be slackened to
allow a free action of the tube C upon a change of temperature, at the samo
time keeping the clip tight upon the tube C; L, a steel spring, at the bottom
of the glass cylinder for the extremity of the cone D to rest in, to prevent
lateral motion; M, the line, shewing the height of mercury at mean tem-
perature.
In witness whereof, I, the said John Gottlieb Ulrich, have hereunto
set my hand and seal, this Tenth day of July, in the year of our Lord
One thousand eight hundred and fifty-six.
Witness,
FRED HARRIS.
JOHN GOTTLIEB ULRICH. (L.S.)