Year: 1887

page_text: Date of Application, 28th Feb., 1887
Complete Left, 28th Nov., 1887
Complete Accepted, 3rd Feb., 1888
Partly a communication_from_abroad by JOHN MILNE, F.G.S., of the Imperial
University, Tokio, Japan, Professor of Geology and Mining..
I, THOMAS GRAY B.Sc., F.R.S.E. of the Physical Laboratory The University
Glasgow in the County of Lanark Physicist and Telegraph Engineer, do hereby declare
the nature of this invention to be as follows:-
This Invention relates to apparatus for registering and recording Earthquakes
Earth tremors and changes of level of the Earth's surface-strata and more particularly
to that type of apparatus known as Gray and Milne's Seismograph. This Seismo-
graph was designed to record in conjunction with a time record, the motions of the
earth during an Earthquake, while it could also by means of a special adjustment, be
made to measure slow changes of ground level.
The apparatus was so constructed as to give a record in the form of three rect-
angular components, one of which was vertical. The device employed to record the
vertical component consisted of a lever supported in a horizontal position carrying a
weight at one end and furnished at the other end with a knife edge. The lever and
weight were supported by means of a spring or springs having an upward pull causing
the knife edge to press against the top of an inverted V groove.
The horizontal lever was made to actuate an index carrying a pen or a sharp point
for writing the record in ink or on a smoked surface as the case may be. In order to
record the horizontal components two pendulums cach consisting of a sufficiently
heavy mass supported by a fine wire or thread were used. The bobs of these
pendulums were held at a distance from their normal position under the action of
gravity by means of horizontal struts furnished with vertical knife edges at their ends
which were made to rest against the bottom of vertical V grooves fixed to the frame-
work at points nearly vertically under the points of suspension of the pendulums in

page_text: such a way that the masses were free to turn round these knife edges. The struts
were arranged so that their lengths lie at right angles to each other, and each was
made to act on an index lever and recording pen or point in the manner hereinbefore
referred to in connection with the vertical component apparatus. The time of
occurrence was obtained by means of a clock which was made to mark at regular
intervals on the record receiving surface. The record receiving surface was generally
either a sheet of paper covering the surface of a cylindrical drum or a continuous
ribbon of paper which was fed forward over the surface of such a drum. Various
contrivances have been used for the purpose of adding to the considerable positive
stability of the herein before described device for registering or recording the vertical
component, sufficient negative stability to render the free period of oscillation of the
lever considerably longer than the period of vibration of the earthquake, but each of
these contrivances have left much to be desired in practical work. An Improved
contrivance for this purpose constitutes part of the present Invention.
These Improvements in and relating to the hereinbefore described apparatus consist
in a modified construction and arrangement of the apparatus and in the addition and
adaptation thereto of other devices parts or details.
Time is marked on the paper, ribbon, or other receiving surface by raising or
lowering the end of a light index carrying a pen, preferably a fine glass siphon, an
end of which is in contact with the surface to be marked, and the other dipping into
an ink well suitably placed for that purpose. This is accomplished by attaching to
the wheelwork of a clock a toothed wheel, by raising and lowering the end of a lever,
or a weight attached to a cord, which is in connection with the index carrying the
pen, causes that pen to rise and fall at regular, or known, intervals of time. The
writing index is attached at a point nearer to or further from its marking end, to a
second lever the end of which is connected by a suitable link to the armature of an
electro-magnetic vibrator. This vibrator is intended to be automatically brought into
action at the time of an earthquake shock and through the lever connection herein-
before referred to or by some other equivalent device is made to record equal short
intervals of time along the record sheet. The index or pen lever is thus connected or
hinged at two points unequally distant from the writing point to two levers, one or
both of which may be in motion, in such a way that the motions of the index due to
the motion of any one of these levers takes place round the other lever as fulcrum.
The record receiving surface may be a continuous band of paper which is being
continuously pulled past a set of marking pens, or alternatively, it may be a sheet of
paper covering a cylinder, or as another alternative, it may be a glass or metal
cylinder covered with carbon deposited from smoke or other suitable substance for
marking upon. When the continuous band or ribbon of paper is used it is, in
preference by clockwork mechanism, kept continuously in motion at a very slow rate
past a set of recording pens, one convenient form of which is a fine glass siphon
taking ink from an ink well. When the record receiving surface is a cylinder
covered with paper or a smoked cylinder it is preferably arranged to have a
slow motion in the direction of its axis so that the record takes the form of a spiral
round the cylinder. At the time of an earthquake shock the rate at which the paper
is pulled forward is automatically very much increased by means of an apparatus
which is actuated by the shaking of the ground. The change of speed is-accomplished
either by causing, by any convenient form of change-wheel arrangement, the length
of the wheel train between the driving power and the governor to be shortened; or
by including two governors in the train of clockwork, one of which is placed at a
point in the train nearer to the driving power than the other, and when the speed is
to be increased throwing out of gear the most distant governor. This change-wheel
or other arrangement is actuated either by an electro-magnet the circuit of which is
closed by the shaking and after a sufficient interval is again broken by the mechanism;
or by a mechanical arrangement such for example as by causing the shaking to make
a ball roll from the end of one pivoted lever on to the end of another. The loss of
weight from the end of the one lever may then allow it to rise and put into gear a
train mechanism to be used for the purpose of re-adjustment, while the gain of weight

page_text: on the end of the other lever may depress it and change the wheelwork or throw out
of gear a governor. After a fixed time the adjusting mechanism may be arranged to
so lower the end of the first lever that the ball again rolls on to it, thus allowing the
wheelwork to be changed back to its slow speed. After this it may raise the ball to
its original position and by the mechanism slipping out of gear at this stage leave it
there in readiness to be again acted upon by the next shock.
The pendulums for controlling the motion of the recording pens which write the
two horizontal components are arranged so that the deflection of the bob can be varied
through somewhat wide limits, and this is combined with light cranked levers to
which the writing pens are attached. The relative .lengths of the two arms of the
cranked levers can also be varied and in this way the record of the motion of the
earth may be either on a magnified or on a diminished scale thus giving a power of
adjustment which has not previously been provided for in this class of apparatus.
The apparatus for adding negative stability to the lever which is used for controlling
the pen which writes the record of the vertical motion consists of one
or more but
preferably of two springs, the points of attachment of which are nearly vertically
above the knife edge fixed to the end of the horizontal lever but so arranged that one
is slightly in front while the other is slightly behind the vertical plane through that
knife edge. This allows the position of the writing pen to be readily adjusted by
slightly increasing the pull on one of the springs and at the same time if necessary
diminishing the pull on the other. As an alternative method of obtaining this
adjustment the points of attachment of the springs may be provided with a screw
adjustment so that they can be moved backward or forward as required.
For measuring slow changes of level of the ground this apparatus or its equivalent
in a simplified form is adjusted to give great magnification and, in order to avoid
friction in producing the record, the pen is either made to vibrate in such a way as
only to touch the record at short intervals thus making a close series of dots instead
of a continuous line, or as an alternative the recording pen may be a metal point from
which a series of electric sparks are made to pass through the paper to the metal
drum, thus perforating the paper with a close series of holes which may be rendered
visible by using the paper as a stencil plate for printing, or in any other convenient
manner. As an alternative apparatus for the purpose of recording the change of
level of the ground an ordinary simple pendulum provided with a single vertical
multiplying lever may be used and the two components obtained by drawing two
ribbons of paper past its point in directions at right angles to each other; the electric
sparks being allowed to pass through both at the same time.
Dated this 25th are at Wahoo
A D 1007

page_text: In part a communication to me from abroad by JOHN MILNE, F.G.S., of the Imperial
University, Tokio, Japan, Professor of Geology and Mining.
I, THOMAS GRAY, B.Sc.. F.R.S.E. of the Physical Laboratory The University
Glasgow in the County of Lanark Physicist and Telegraph Engineer, do hereby
declare the nature of this invention, and in what manner the same is to be performed,
to be particularly described and ascertained in and by the following statement:-
This Invention relates to apparatus for registering and recording Earthquakes,
Earth tremors and changes of level of the Earth's surface strata and more particularly
to that type of apparatus known as Gray and Milne's Seismograph. This Seismo-
graph was designed to record in conjunction with a time record, the motions of the
earth during an Earthquake while it could also by means of a special adjustment be
made to measure slow changes of ground level. The apparatus was so constructed as
to give a record in the form of three rectangular components, one of which was
vertical. The device employed to record the vertical component consisted of a lever
supported in a horizontal position carrying a weight at one end and furnished at the
other end with a knife edge. The lever and weight were supported by means of a
spring or springs having an upward pull causing the knife edge to press against the
top of an inverted V groove.
This horizontal lever was made to actuate an index carrying a pen or a sharp point
for writing the record in ink or on a smoked surface as the case may be. In order to
record the horizontal components two pendulums each consisting of a sufficiently
heavy mass supported by a fine wire or thread were used.
The bobs of these pendulums were held at a distance from their normal position
under the action of gravity by means of horizontal struts furnished with vertical
knife edges at their ends which were made to rest against the bottom of vertical
V grooves fixed to the frame work at points nearly vertically under the points of
suspension of the pendulums in such a way that the masses were free to turn round
these knife edges. The struts were arranged so that their lengths lie at right angles
to each other, and each was made to act on an index lever and recording pen or
point in the manner hereinbefore referred to in connection with the vertical com-
ponent apparatus. The time of occurrence was obtained by means of a clock which
was made to mark at regular intervals on the record receiving surface. The record
receiving surface was generally either a sheet of paper covering the surface of a
cylindrical drum or a continuous ribbon of paper which was fed forward over the
surface of such a drum. Various contrivances have been used for the purpose of

page_text: adding to the considerable positive stability of the herein before described device for
registering or recording the vertical component, sufficient negative stability to render
the free period of oscillation of the lever considerably longer than the period of vibra-
tion of the Earthquake, but each of these contrivances have left much to be desired
in practical work. An improved contrivance for this purpose constitutes. part of
the present Invention.
These Improvements in and relating to the hereinbefore described apparatus consist
in a modified construction and arrangement of the apparatus and in the addition
and adaptation thereto of other devices parts or details.
Time is marked on the paper, ribbon or other receiving surface by raising or
lowering the end of a light index carrying a pen, preferably a fine glass syphon, one
end of which is in contact with the surface to be marked, and the other dipping into
an ink well suitably placed for that purpose. This is accomplished by attaching to
the wheel work of a clock a toothed wheel which by raising and lowering the end of
a lever, or a weight attached to a cord which is in connection with the index carrying
the pen, causes that pen to rise and fall at regular or known intervals of time. The
writing index is attached at a point nearer to or further from its marking end, to a
second lever the end of which is connected by a suitable link to the armature of an
electro-magnetic vibrator, or it may be operated by means of a ratchet wheel and
clock work. This vibrator is intended to be automatically brought into action at the
time of an Earthquake shock and through the lever connection herein before referred
to or by some other equivalent device is made to record equal short intervals of time
along the record sheet.
The index or pen lever is thus connected or hinged at two points unequally distant
from the writing point to two levers one or both of which may be in motion, in such
a way that the motions of the index due to the motion of any one of these levers
takes place round the other lever as fulcrum.
The record receiving surface may be a continuous band of paper which is being con-
tinuously pulled past a set of marking pens, or alternatively, it may be a sheet of paper
covering a cylinder, or as another alternative, it may be a glass or metal cylinder
covered with carbon deposited from smoke or other suitable substance for marking upon.
When the continuous hand or ribbon of paper is used it is, in preference by clockwork
mechanism, kept continuously in motion at a very slow rate past a set of recording pens,
one convenient form of which is a fine glass syphon taking ink from an ink well. When
the record receiving surface is a cylinder covered with paper or a smoked cylinder it is
preferably arranged to have a slow motion in the direction of its axis so that the record
takes the form of a spiral round the cylinder. At the time of an earthquake shock the
rate at which the paper is pulled forward is automatically very much increased by means
of an apparatus which is actuated by the shaking of the ground. The change of speed
is accomplished either by causing by any convenient form of change-wheel arrange-
ment, the length of the wheel change between the driving power and the governor to
be shortened; or by including two governors in the train of clockwork one of which
is placed at a point in the train nearer to the driving power than the other, and when
the speed is to be increased throwing out of gear the most distant governor. This
change-wheel or other arrangement is actuated either by an electro-magnet the
circuit of which is closed by the shaking and after a sufficient interval is again
broken by the mechanism, or by a mechanical arrangement such for example as by
causing the shaking to make a ball roll from the end of one pivoted lever on to the
end of another. The loss of weight from the end of the one lever may then allow. it
to rise and put into gear a train mechanism to be used for the purpose of readjustment,
while the gain of weight on the end of the other lever may depress it and change the
wheelwork or throw out of gear a governor. After a fixed time the adjusting
mechanism may be arranged to so lower the end of the first lever that the ball again
rolls on to it, thus allowing the wheel work to be changed back to its slow speed;
after this, it may raise the ball to its original position and by the mechanism slipping
out of gear at this stage leave it there in readiness to be again acted upon by the
next shock.

page_text: The pendulums for controlling the motion of the recording pens which write the
two horizontal components are arranged so that the deflection of the bob can be
varied through somewhat wide limits, and this is combined with light bellcrank levers
to which the writing pens are attached. The relative lengths of the two arms' of the
bellcrank levers can also be varied and in this way the record of the motion of the
earth may be either on a magnified or on a diminished scale thus giving a power of
adjustment which has not previously been provided for in this class of apparatus.
The apparatus for adding negative stability to the lever which is used for controlling
the pen which writes the record of the vertical motion consists of one or more but
preferably two springs, the points of attachment of which are nearly vertically above
the knife edge fixed to the end of the horizontal lever but so arranged that one is
slightly in front while the other is slightly behind the vertical plane through that knife
edge. This allows the position of the writing pen to be readily adjusted by slightly
increasing the pull on one of the springs and at the same time if necessary diminishing
the pull on the other. As an alternative method of obtaining this adjustment the
points of attachment of the springs may be provided with a screw adjustment so that
they can be moved backward or forward as required.
For measuring slow changes of level of the ground, this apparatus or its equivalent
in a simplified form is adjusted to give great magnification, and, in order to avoid
friction in producing the record, the pen is either made to vibrate in such a way as
only to touch the record at short intervals thus making a close series of dots instead
of a continuous line; or as an alternative, the recording pen may be a metal point
from which a series of electric sparks are made to pass through the paper to the
metal drum, thus perforating the paper with a close series of holes which may be
rendered visible by using the paper as a stencil plate for printing, or in any other
convenient manner. As an alternative apparatus for the purpose of recording the
changes of level of the ground, an ordinary simple pendulum provided with a single
vertical multiplying lever may be used and the two components obtained by drawing
two ribbons of paper past its point in directions at right angles to each other; the
electric sparks being allowed to pass through both at the same time.
In order that our Invention may be properly understood and carried into practical
effect I will now proceed to describe more particularly the mode or manner in or
according to which the same is or may be accomplished, reference being had to the
accompanying drawings and to the letters and figures marked thereon.
For
Fig. 1, is an elevation of one form of the complete apparatus in which the different
parts are fixed to the same sole plate and so connected together that the whole of the
operations hereinafter described can be accomplished by mechanical means.
greater clearness and simplicity some unimportant details such as parts of the wheel-
work train for driving the paper ribbon or record-sheet to be hereinafter more
particularly described, are omitted.
Figure 2, is a plan of the instrument which is shown in elevation in Figure 1.
Figure 3, is an explanatory diagram illustrating the action of the change-speed and
time registering apparatus shown in position in Figures 1, and 2, and hereinafter
described with reference to those figures.
Figure 4, is an elevation of a simpler form of apparatus for recording the horizontal
components of earthquake motion especially adapted for very small motions, either.
slow changes of level or rapid tremors of the earth's surface.
Figure 5, is a sectional plan of the apparatus shown in elevation in Figure 4.
Figure 6, is an enlarged view of part of the elevation shown in Figure 4.
Time is marked on the paper ribbon a Figures 1, and 2, or other suitable record
receiving surface by raising or lowering the end of a light index b Figures 2 and 3,
carrying a pen, preferably a fine glass or syphon, one end of which is in contact withi
the paper ribbon while the other dips into an ink well e suitably placed for that
purpose. This is accomplished by attaching to the wheel work of a clock, such as
that shown on d Figs. 1, and 2, a toothed wheel e, Figure 3, which, by raising or
lowering one end of a lever f. fulcrummed at y, the other end of which is connected to
the pen lever b, causes the pen to rise and fall at regular and, or, known intervals of.

page_text: time, as for example every five minutes which will be the case if the wheel makes one
turn in one hour. The writing index or pen lever is attached at a point nearer to
or further from its marking end to a second lever g Figures 2 and 3. The lever g is
pivoted at one end and it may either be connected by a link to or from the armature
of the electro-magnet of an electro magnetic vibrator similar in principle to vibrators
in common use for ringing electric bells and other purposes, or it may be acted on in
the manner shown in Figs. 2 and 3, by a ratchet wheel driven by clockwork at a
uniform rate, by either of which means the end of the lever g is caused to rise and
fall at regular intervals, which in the arrangement shown in the drawings may be
conveniently made of one second duration, but in the electro-magnetic vibrator may
be much shorter. The lever g is brought into action at the time of an earthquake by
means of the change speed apparatus hereinafter described, which raises one end of
the lever i Figures 1, 2, and 3, and lowers the other end, thus allowing the end of the
lever g to fall on the edge of the ratchet wheel h, on which it rests for such time as the
change speed apparatus holds the lever i out of contact with it. The index or pen
lever is thus connected or hinged at two points unequally distant from the writing
point to two levers, one or both of which may move, in such a manner that the
motion of the index due to any one of these levers takes place round the other as a
fulcrum.
The record receiving surface may be a long band of paper which is continuously
pulled past a set of marking pens, or alternatively it may be a sheet of paper covering
à cylinder, or as a further alternative, it may be a glass or metal cylinder covered
with carbon deposited from smoke, or other suitable substance for marking upon.
When the record receiving surface is a cylinder it is preferably arranged so as to
have either a slow continuous motion, or a motion taking place at fixed intervals, in
the direction of its axis, so that the record takes the form of a spiral or of a stepped
line round the cylinder. The motion in the direction of the axis of the cylinder is
readily obtained by screwing the spindle of the cylinder and causing it to work in a
fixed nut or in a bush furnished with a projecting tongue which fits the thread of
the screw.
In the form of the apparatus shown by the accompanying drawings the record
receiving surface is a long band of paper a, Figures 1 and 2, with its plane vertical,
pulled slowly past a set of recording pens or syphons j k l supplied with ink by the
ink wells m n o, figures 1 and 2 by means of clockwork mechanism partly shown in
position under the paper drums. The paper is unwound from a supply drum A from
which it passes round a drum B to a third drum Chereinafter called the "haul-off
drum." The drum B is kept moving at a uniform rate by means of the train of
clock work hereinbefore referred to, which is preferably driven by a cord and weight
from the drum D. The mode or manner of regulating the rate of motion of this
clockwork is hereinafter more particularly described in connection with the change
speed mechanism. Tension is kept on the paper by means of another train of clock-
work beginning at the driving drum E and terminating in the "Haul-off" drum C.
The drums A and C are preferably made so as to be interchangeable so that C when
full may be substituted for A by unscrewing the screws H and F, which hold these
drums in their places and act as the upper pivots round which they turn. At the
time of an earthquake shock the rate at which the paper is pulled forward is auto-
matically increased by means of an apparatus which is actuated by the shaking of the
ground. This may be accomplished in several ways, as for example by any one of
those which are described in the earlier part of this Specification. One method is
shown in detail in the accompanying drawings Figures 1, 2, and 3. According to
this method a ball, or a cylinder, p is supported in sufficiently nearly neutral equili
brium on a pivoted platform q which is supported on the end of a lever pivoted at s
and the weight of the ball is counterpoised by a weight t. At the time of an earth-
quake the shaking causes the ball or cylinder p to roll from the platform q on to
another platform u upon the end of another lever v which is pivoted at w. The weight
of the ball or cylinder p causes the end of the lever on which it rolls to be depressed
and the other end to rise, carrying with it a wheel x, figure 3, forming part of the

page_text: train of wheelwork driving the paper. The raising of the wheel x takes it out of gear
with the pinion y by which it drives the distant governor hereinafter described and
hence allows the part of the train of mechanism nearer to the driving weight than
to run on by itself. Two governors of any suitable design but generally of the form
known as Thomson's Spring Governors" are included in the train of mechanism,
one of them between the driving drum and a, and the other further from the driving
drum than x. The effect of breaking the train of mechanism by raising the wheel
in the manner hereinbefore described is to leave out the distant governor and thus to
allow the mechanism to run at a faster rate regulated by the adjustinent of the nearer
governor. Simultaneously with this change of speed the lever allows the lever g to
fall on the edge of the wheel h and by its action to record short intervals of time on
the paper band, thus giving the means of telling the speed of the paper at any instant.
In order that the speed may after a sufficient interval be reduced to its original slow
rate, the lever when relieved of the weight p turns under the weight of the counter-
poise and carries with it or pushes down a wheel, the weight of which is carried
by a spring placed under the end of the arbor, putting it into gear with a pinion a',
which forms part of the driving train. This wheel as it turns round carries with it a
cam b', which gradually raises the end of the lever on which t is fixed, lowering at
the same time the platform y. When the platform becomes lower than the plat-
form the ball or cylinder p runs back on to which is afterwards gradually raised
by the cam b', to its normal position and left balanced by the wheel z passing out of
gear with the pinion a'. The lever follows the motion of the lever and at a certain
stage brings the wheel into gear with the pinion y and reduces the speed. The
change speed apparatus hereinbefore described is also applicable to cases where the
initial motion is zero, the only difference being that instead of putting the wheel
out of gear with the pinion y, the distant governor is dispensed with and a brake or
catch acting on the other governor is substituted for the wheel .. This form of
apparatus is preferred when the record receiving surface is a smoked cylinder or
other limited surface such as those herein before referred to.
7'
The horizontal components of the motion are recorded by means of two masses c', d',
figures 1 and 2, which form the bobs of two pendulums supported by a wire as shown
at e, figure 1. The pendulums are deflected to any desired extent, so as to give the
requisite sensibility or render the instrument capable of recording motions of the
requisite magnitude, by sliding the bobs cd, along struts f, g, at any point of
which they can be clamped. They actuate the syphon pens j, k, by means of light
connecting rods ',, which are hinged to the struts f, g, and terminate in small
hollow cones k¹, which rest on needle points carried by the vertical arms of the
bellcrank levers j³, 3. The position of the needle points on the arm of the pen lever
is adjustable so that magnification or diminution of the actual motion in the record
may be varied. The vertical arnis of the bellcrank levers j³, k³, are hinged at their
upper ends so as to allow free motion at right angles to the plane of the crank. The
struts f, g, terminate in vertical knife edges and the position of the point of suspen-
sion of the pendulum c, d, can be made to lie in the vertical plane through the
desired position of the bob and the knife edge, by adjusting the position of the pulley m
to one side or other by screwing along the bearing shaft n'. The period of free vibra-
tion of the pendulum is adjusted to any desired value by moving the forks o', backwards
or forwards by means of the nuis p'. The struts are adjusted to the horizontal position
by winding or unwinding the wire e¹, on the drums 7', by the worm and
pinion ¹.
The vertical component of the motion is recorded by a pendulum which consists of
a horizontal lever s carrying at its outer end a cylindrical mass t¹, resting at its other
end through two knife edges in the hollows of two inverted V grooves at u', and
supported by two flat springs which are nearly straight when free, but are of such
a variable breadth that when supporting the lever they bend nearly into circles, thus
equally straining every point of the spring. This arrangement provides a horizontal
lever pendulum having a moderately long period of free vertical vibration, which may
be used by itself for recording the vertical components of earthquake motion especially

page_text: motions of short period, but is preferably provided with one or more, generally
two, light spiral-springs w¹ attached at their lower ends to adjusting screws and at
their upper ends to a light cross bar y placed vertically above the knife edges for the
purpose of increasing its period of vibration. The attachment of the spiral springs to
the cross bar y is made at such a height above the knife edges at u¹, that when the
elongation of the spiral springs is equal or slightly under that distance the horizontal
pendulum is in nearly neutral equilibrium. The stability is regulated by the screws a
at the bottom of the springs. This pendulum actuates by means of a link ¹, attached
to the cross bar a² a light pivoted lever which carries a fine glass syphon, one end of
which dips into the ink well m, and the other end rests lightly against the band of
paper and writes the record.
The springs wherein before referred to, for increasing the period of vibration of the
vertical motion pendulum, may also be utilized for adjusting the position of that
pendulum either by placing the point of attachment of one in front of, and of the
other behind, the vertical plane through u, when variations of the tension of the
springs will change the position of the horizontal lever of the pendulum, or by pro-
viding a means of changing the point of attachment forward or backward by attaching
it to a horizontal screw.
For measuring slow changes of level of the ground or for recording very minute
motions, this apparatus or its equivalent in a simplified form is adjusted to give great
magnification and, in order to avoid friction in producing the record, the pen is either
made to vibrate in such a way as only to touch the record at short intervals, thus
making a close series of dots instead of a continuous line, or as an alternative, the
recording pen may be a metal point from which a series of electric sparks are made
to pass through the paper to the metal drum, or other metal backing placed below
the paper, thus perforating the paper with a close series of holes, the line of which
will show the motions of the point. As an alternative especially applicable to the
measurement of slow changes of level, I sometimes prefer to cause the record receiving
surface to approach and recede from the pen at regular intervals, thus leaving the pen
free of friction for a sufficient time to assume its position of equilibrium.
One form of the simplified apparatus for recording slow changes of level of the
ground or for recording minute motions of the ground is shown in Figures 4, 5,
and 6. It consists of a mass & supported by a wire c² from a metal plate d which for
electric insulation rests on a vulcanite or other insulating plate which rests on the
top of a suitable frame. The mass 2 actuates a magnifying lever through a needle
point or other suitable universal joint g. The lever is supported on another needle
point or universal joint attached to or resting on a spring carried in an adjustable
manner on a stand and the pressure of which can be adjusted by a screw . Electric
sparks are made to pass from the point of the lever through two bands of paper
to a metal plate m². The paper passes over pulleys or drums at n² ² p² ² and is
driven by clockwork. The electric current passes through the pointer or through
a light wire attached thereto by electrodes 2 (2 connected to an induction coil or
other source of electricity of high tension and the record is to be made visible by
holding the paper between the eye and the light, or by using it as a stencil plate or in
any other convenient manner.
The pointer is balanced round its point of support by means of a heavy disk u²
so as to prevent it adding stability to the pendulum. In some cases I prefer to make
the pointer top-heavy either by making u² heavier than is necessary to simply produce
a balance, or by placing it on a continuation of the pointer carried above the upper
pivot or universal joint. In such cases it is desirable to so distribute the masses on
the pointer that the upper joint q will be nearly enough the instantaneous axis of
rotation of the pointer, when it receives an impulse at the lower or supporting pivot.
The object of making the pointer f top-heavy is to increase the period of oscillation
of the pendulum.
I desire it to be understood that I do not limit myself to the precise details and
arrangements hereinbefore described and illustrated by the accompanying drawings
since these may be varied without departing from the said Invention.

page_text: Having now particularly described and ascertained the nature of the said Inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
(1) In seismographic apparatus; the combination of the mechanism for driving
the record receiving surface and automatically changing the rate of motion of that
surface or for starting it from rest, with mechanism for automatically restoring the
speed and the automatic apparatus to its original condition; substantially as herein-
before described and as illustrated by the accompanying drawings.
(2) In seismographic apparatus; a pendulum for recording a horizontal component
of earthquako, motion so constructed and arranged that its sensibility may be changed
or varied either by altering the position of the pendulum bob on a strut, or by altering
on the recording lever, the point of application of the rod connecting the pendulum
to the recording lever, or by altering both of these elements; substantially as herein-
before described.
(3) In seismographic apparatus; mechanism for adjusting the point of suspension
of the pendulum referred to in the preceding claiming clause (2); constructed and
arranged substantially as herein before described.
(4) In seismographic apparatus; the horizontal lever pendulum for recording the
vertical component of earthquake motion in combination with the peculiarly formed
supporting springs which are shaped so as to be equally bent at every part, when
supporting a lever, and with the springs for increasing the period of vibration of the
pendulum; substantially as hereinbefore described.
(5) In seismographic apparatus; the mechanism for marking time upon the record
receiving surface whereby one writing pen is made to record the motions of two levers;
substantially as herein before described.
(6) In apparatus for recording slow changes of level of the earth; devices for
eliminating the effect of the friction of the recording pen, constructed arranged and
operated so as to cause the record receiving surface to touch the pen at intervals only;
substantially as described.
(7) In seismographic apparatus; the application of mass to the top of a vertical
magnifying lever actuated by the bob of an ordinary pendulum, for the purpose of
increasing the period of vibration of the pendulum; substantially as herein before
described.
331
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