IMPROVE- MENTS IN ELECTRIC TELEGRAPHS."
Year: 1865

page_text: LETTERS PATENT to William Thomson, of Glasgow College, Doctor of
Laws and Professor of Natural Philosophy in the University and College
of Glasgow, and Cromwell Fleetwood Varley, of Fleetwood House,
Beckenham, in the County of Kent, for the Invention of "IMPROVE-
MENTS IN ELECTRIC TELEGRAPHS."
of Glasgow, and Cromwell Fleetwood Varley, of Fleetwood House,
Beckenham, in the County of Kent, for the Invention of "IMPROVE-
MENTS IN ELECTRIC TELEGRAPHS,'
Sealed the 22nd December 1865, and dated the 6th July 1865.
PROVISIONAL SPECIFICATION left by the said William Thomson and
Cromwell Fleetwood Varley at the Office of the Commissioners of
Patents, with their l'etition, on the 6th July 1865.
We, WILLIAM THOMSON, of Glasgow College, Doctor of Laws and Pro-
fessor of Natural Philosophy in the University and College of Glasgow, and
CROMWELL FLEETWOOD VARLEY, of Fleetwood House, Beckenham, in the
County of Kent, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN ELECTRIC TELEGRAPHS," to be as follows:-
This Invention has for its object improvements in electric telegraphs. In
order to transmit signals of short duration through long submarine telegraphic
lines with great rapidity and distinctness, we arrange apparatus in such
manner that each time the operator puts down a finger key, or acts on an
instrument equivalent to a finger key, the apparatus will automatically send

page_text: into the line in rapid succession three or a greater number of currents of
equal strength alternately positive and negative, but of unequal duration.
The first current corresponds in sign with that which it is desired should
arrive at the other end of the line, the second is of opposite sign, and the
third is of the same sign as the first current. When three currents are-
employed to produce one signal the duration of the second current should
exceed that of the first, and the duration of the third current should be less
than that of either the first or second. If more than three currents are
employed to produce a single current and signal at the distant end of the line,
the fourth current will be opposite in sign to the third, the fifth opposite to
the fourth, and so on. The first current sent causes a rapid change in the
electrical state of the conductor, but if it werealone and uncorrected it would
on arriving at the distant station occupy the receiving instrument for a con-
siderable time, and produce on it a stronger effect than is desired; therefore,
to cut it off (so to speak), and leave only the effect required, electricity of
opposite sign is thrown into the wire, and in order that this second current
may have power to operate as rapidly as possible in overcoming the first
current, the second current is continued on so long that if uncorrected it
would produce an effect beyond that required of it in checking the first
current, and so the second current is in turn corrected by a third current, and
this again may be corrected by a fourth, and so on theoretically to any
number; but from five to seven currents are, we believe, as many as are prac-
tically required in such a cable as the present Atlantic. Whatever be the
number of currents employed to produce a single indication, it is essential that
the currents which correspond in sign with the single current which is desired
to arrive at the distant station should in the sum of their durations exceed
the currents of opposite sign. If it be desired to produce at the distant end
of the line a signal of some duration, corresponding with say a line in Morse's
alphabet, it may be done on the same principle by increasing the duration of
the several currents and somewhat altering their proportions, thus an indica-
tion of greater strength and somewhat longer duration is obtained; or with-
out increasing the strength of the indication its duration may be prolonged by
introducing a series of rapidly alternating currents so proportioned as to main-
tain the current at the distant end of the strength required. Thus it will be
seen that a transmitting instrument may be constructed to send into a tele-
graphic line combined currents as above described suitable to give at the
further end of the line four distinct signals, viz., 1, a feeble signal of short
duration and positive sign; 2, a similar signal of negative sign; 3,a signal of
greater strength or duration, or both, and positive sign; and 4, a signal similar

page_text: to that last mentioned and negative in sign. Similarly an instrument may be
made to give combined currents for signals of three or even a greater number
of different strengths or durations.
We prefer to arrange the instrument for sending these or similar succes-
sions of currents automatically at the required intervals in the following
manner: The apparatus consists of an axle driven as nearly as may be at a
uniform rate, and it carries one or more cams, and each cam is free to move
on the axle. On the axle there are (for each cam) two discs of metal, and
on the cam a disc of similar size. A spring presses the disc on the cam
against one of the discs fixed on the moving axle. Between these discs a
piece of oilel leather or other suitable material is placed so that the cam is
driven by friction, and its stoppage does not stop the rotation of the axle. A
detent by falling into a notch prevents the cam from rotating. The other end
of the spring before mentioned that presses the cam also presses against a
disc whose edge is cut into the form of a ratchet wheel. This latter disc is
separated from the fixed disc on the axle also by a disc of oiled leather.
There is a second detent taking into the teeth of this wheel, and so arranged
that when the former detent is lifted the latter detent falls into the ratchet
wheel. Thus the friction opposing the motion of the machine is equalized so
as to remain nearly the same whether the cam be running or not. Or this
method of equalizing the friction may be dispensed with if a sufficiently
powerful governor be applied in connection with the rotating axis. When the
key is pressed down the detent is lifted and the cam rotates until the key is
lifted and the cam has returned to its starting point, assuming that one revo-
lution of the cam corresponds with one signal (because in some instauces it
becomes advisable to use half or other submultiple of the revolution of the
cam to produce a signal). This cam either carries a number of properly
insulated contact picces or projections acting upon springs or levers by which
in moving through one revolution or submultiple of a revolution as aforesaid
it produces alternately contacts of varying lengths as already mentioned.
The precise lengths of these contacts depend upon the length of the
line to be worked and many other conditions. If it be desired to work with
an alphabet on the Stenheil principle one cam only may be used with two
keys and a current reverser, so that in pressing down the right-hand key such
signals are produced as will correspond to say a positive current at the
distant end of the line, while if the left-hand key be pressed down the
connections being reversed, currents of similar duration but opposite names
are sent through the line to produce a negative signal at the distant end.
Also if it is desired the strength of these signals may be varied by varying

page_text: the battery power; for this purpose four keys may be combined with one cam
two keys working with the feeble power and giving positive and negative
signals respectively, and the other two keys working similarly with the stronger
battery power. If it is desirod to work with an alphabet on the Morse
principle, two keys are employed, one key releases a cam which produces a
dot, the other key releases another cam which produces a dash, and in this
case, and generally where it is desired to give signals of different durations,
the cams should be on different axes with different speeds of rotation, or some
equivalent arrangement should be resorted to, and mechanism should also be
applied, so that when a key of any cam is down no other key can go down.
A spring or click may be combined with each cam in such manner that when
the cam revolves it lifts the spring or click by a snail on the cam so as to
give audible notice when the rotation of the cam is nearly completed by
dropping off the end of the snail, and this informs the operator when he may
begin to make a fresh signal; or other equivalent mechanism may be employed
to give this audible notice. The speed of the machine is controlled by a fly
or other suitable appliance to produce a rate of rotation. as uniform as may
be. In place of arranging the cams to travel intermittently, they may be
kept revolving continuously but without sending currents into the telegraphic
line until the key is depressed and the apparatus connected with the key is so
arranged that at whatever time during the rotation of the axis the key is put
down, it commences to act only at the starting point of the cam, and continues
to act until all the currents required for the signal have been sent into the
line. In some cases we allow the cams to act continuously on their springs
or levers, and then the key acts to put the springs or levers belonging to its
cam into the telegraphic circuit at the commencement of the signal and to
take them out at the end thereof; or the springs or levers may be kept out
of contact with the cams except when their keys are depressed; in this latter
case the same operation of throwing the train of contacts for the particular
cam into the telegraphic circuit ought to be performed as in the first case, to
obviate the objection of leaving more contacts in the telegraphic circuit than
necessary. If desired the cams may be so constructed as each to send into
the line combined currents suitable to produce two or more currents at the
distant station, for instance so as to indicate a particular letter corresponding
with the key employed. Also in place of cams it is evident that cylinders to
receive moveable type, like projections may be employed, or type may be
assembled on a flat surface having a motion given to it to carry the type
under springs or levers such as those on which the cams are described to act:
Each type will have several projections on it suitable for sending into the

page_text: telegraphic line combined currents such as to produce either one, two, or
several currents at the distant end of the line.
We would remark that in the Specification of a former Patent granted to
one of us, viz., to me the aforesaid William Thomson, bearing "date the
20th February, 1858, No. 529, there is described methods of producing
signals through a long submarine telegraphic line which are to some extent
analogous to those hereinbefore described. According to one of these methods'
a signal was produced by sending into the line.wire for a given time, say for
one second, a current of a certain strength (call it 48) then for another.
second there was sent into the line wire a current of opposite sign, of greater
strength, say 50, and lastly for a third second there was sent into the wire a
current of the same sigu as the first, with a strength of say 12. In this way
the result required was approximately obtained, but the methodisinconvenient
requiring as it does the use of three different strengths of electricity besides
which the use of the weaker currents involves a loss of time. There is also"
a simpler arrangement described in the same Specification; it consists in
sending first a current of the same sign as that which is intended to arrive at
the further end of the line, and then another current of opposite sign and
the same strength, but continued for a shorter time so as to neutralize
the excess of the first current. This method is simple, and to some extent
accomplishes its object, but it will not give a speed equal to that given by the
method herein-before described where the duration of the second current
exceeds that required to neutralize the excess of the first, and a subsequent
compensation is made by the use of another current or currents. We would
further remark that three is the greatest number of currents ever heretofore
employed to produce a single indication, and that with very slow cables a
much better effect is obtained by employing according to our Invention
apparatus for sending into the telegraphic line four, five, or a greater number
of currents to produce a single indication.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Thomson and Cromwell Fleetwood Varley in the
Great Seal Patent Office on the 6th January 1866.
TO ALL TO WHOM THESE PRESENTS SHALL COME, wc, WILLIAM
THOMSON, of Glasgow College, Doctor of Laws and Professor of Natural
Philosophy in the University and College of Glasgow, and CROMWELL FLEET-
WOOD VARLEY, of Fleetwood House, Beckenham, in the County of Kent, send
greeting.

page_text: WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Sixth day of July, in the year of our Lord One
thousand eight hundred and sixty-five, in the twenty-ninth year of Her reign,
did, for Herself, Her Heirs and successors, give and grant unto us, the said
William Thomson and Cromwell Fleetwood Varley, Her special licence that
we, the said William Thomson and Cromwell Fleetwood Varley, our executors,
administrators, and assigns, or such others as we, the said William Thomson
and Cromwell Fleetwood Varley, our 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 "Iк-
PROVEMENTS IN ELECTRIC TELEGRAPHS," upon the condition (amongst others)
that we, the said William Thomson and Cromwell Fleetwood Varley, our exe-
cutors or administrators, by an instrument in writing under our or their hands
and seals, or under the hand and seal of one of us or them, 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 Cromwell Fleetwood Varley, on behalf
of myself and the said William Thomson, do hereby declare the nature of the
said Invention, and in what manner the same is to be performed, to be par-
ticularly described and ascertained in and by the following statement thereof,
that is to say:-
This Invention has for its object improvements in electric telegraphs.
In order to transmit signals of short duration through long submarine
telegraphic lines with great rapidity and distinctness, we arrange apparatus in
such manner that each time the operator puts down a finger key or acts on
an instrument equivalent to a finger key, the apparatus will automatically send
into the line in rapid succession three or a greater number of currents of
equal strength alternately, positive and negative, but of unequal duration.
The first current corresponds in sign with that which it is desired should
arrive at the other end of the line, the second is of opposite sign, and the third
is of the same sign as the first current. When three currents are employed
to produce one signal the duration of the second current should exceed that of
the first, and the duration of the third current should be less than that of
either the first or second. If more than three currents are employed to pro-
duce a single current and signal at the distant end of the line, the fourth

page_text: current will be opposite in sign to the third, the fifth opposite to the fourth,
and so on. The first current sent causes a rapid change in the electrical
state of the conductor, but if it were alone and uncorrected it would on
arriving at the distant station occupy the receiving instrument for a consider-
able time, and produce on it a stronger effect than is desired, therefore to
cut off (so to speak) and leave only the effect required, electricity of
opposite sign is thrown into the wire, and in order that this second current
may have power to operate as rapidly as possible in overcoming the first
current, the second current is continued on so long that if uncorrected it
would produce an effect beyond that required of it in checking the first current,
and so the second current is in turn corrected by a third current, and this
again may be corrected by a fourth, and so on theoretically to any number,
but from five to seven currents are we believe as many as are practically
required in such a cable as the present Atlantic. Whatever be the number
of currents employed to produce a single indication it is essential for perfect
compensation that the currents which correspond in sign with the single
current which is desired to arrive at the distant station should in the sum of
their durations exceed the currents of opposite sign. We prefer to arrange
the instrument for sending these or similar successious of currents automati-
cally at the required intervals in the following manner: The apparatus
consists of an axle driven as nearly as may be at a uniform rate, and it carries
one or more cams, and each cam is free to move on the axle. On the axle
there are (for each. cam) two discs of metal, and on the cam a disc of similar
size, a spring presses the disc on the cam against one of the discs fixed on the
moving axle, between these discs a piece of oiled leather or other suitable
material is placed, so that the cam is driven by friction, and its stoppage.does
not stop the rotation of the axle, a detent by falling into a notch prevents the
cam from rotating. The other end of the spring before mentioned that
presses the cam also presses against a disc whose edge is cut into the form of
a ratchet wheel; this latter disc is separated from the fixed disc on the axle
also by a disc of oiled leather. There is a second detent taking into the teeth
of this wheel, and so arranged that when the former detent is lifted the latter
detent falls into the ratchet wheel; thus the friction opposing the motion of
the machine is equalized so as to remain nearly the same whether the cam be
running or not; or this method of equalizing the friction may be dispensed
with if a sufficiently powerful governor be applied in connection with the
rotating axis. When the key is pressed down the detent is lifted and the
cam rotates until the key is lifted, and the cam has returned to its starting
point, assuming that one revolution of the cam corresponds with one signal

page_text: (because in some instances it becomes advisable to use half or other sub-
multiple of the revolution of the cam to produce a signal). This cam either
carries a number of properly insulated contact pieces or projections acting
upon springs or levers, by which in moving through one revolution or sub-
multiple of a revolution as aforesaid it produces alternately contacts of varying
lengths as already mentioned. The precise lengths of these contacts depends
upon the length of the line to be worked, and many other conditions. A
spring or click may be combined with each cam in such manner that when
the cam revolves it lifts the spring or click by a snail on the cam so as to give
audible notice when the rotation of the cam is nearly completed by dropping
off the end of the snail, and this informs the operator when he may begin to
make a fresh signal, or other equivalent mechanism may be employed to give
this audible notice. The speed of the machine is controlled by a fly or other
suitable appliance to produce a rate of rotation as uniform as may be. If it
be desired to work with an alphabet or the Steinheil principle one cam only
may be used with two keys and a current reverser, so that in pressing down
the right-hand key such signals are produced as will correspond to, say, a
positive current at a distant end of the line, while if the left-hand key be
pressed down, the connections being reversed, currents of similar duration but
opposite names are sent through the line to produce a negative signal at the
distant end.
The accompanying Drawing shows the instrument we employ to send
Steinheil signals, that is to say, simple, positive, and negative signals of equal
duration and strength. The axle A, A', is driven as nearly as may be at a
uniform rate, and carries a cam B free to move on the axle. On the
axle A, A', there are two discs of metal, C and C³, and on the cam there is a
corresponding disc D; a spring F presses the disc D of the cam against the
discC, which is fixed on the moving axle. Between these discs a piece of oiled
leather or other suitable material is placed, so that the cam is driven by
friction, and its stoppage does not stop the rotation of the axle. A detent G,
(Figures 1, 2, and 8) by falling into a notchy, prevents the cam from rotating.
The other end of the spring F before mentioned presses against a disc R,
bearing the ratchet wheel a (Figures 1, 4, and 9). The disc R and ratchet
are loose on the axle A, A¹, and are separated from the fixed disc C¹ on the
axle also by a disc of oiled leather. There is a detent b taking into the teeth
of the wheel, and so arranged that when the detent G is lifted free from
the notch g, the detent benters the teeth of the ratchet wheel a. To effect
this the levers forming the detents G and a are pinned to an axle c, d, as
shown in the Drawing, so that band G rise and fall together; thus the friction

page_text: opposing the motion of the machine is equalized, whether the cam be running
or not, for if the cam be stopped there is a retarding friction between C and D,
due to the pressure of the spring F, but no friction between a and C, but if
the cam is running an equal friction occurs between a and C¹, but none
between C and D. The friction of the ends of the spring F is also equal in
the two cases. This method of equalizing the friction may be dispensed with
if a sufficiently powerful governor be applied in connection with the rotating
axis. When either the vulcanite key P or N corresponding to positive and
negative signals is pressed down, the detent G is lifted and the cam B rotates
with the axle A, A', until the key is released, when the spring (Figures 4
and 2) forces the detent G into its notch as soon as the cam has reached its
original position. Each single revolution of the cam B3 makes one signal by
means of the contacts produced by the double set of projections under the
springs el aud . The arrangement of those projections is shown in Figures 5
and 6, and the order in which they act is indicated by the numerals 1, 2, 3,
4, 5, marked upon them. The projections in Figure 5 are under the spring,
and those in Figure 6 under el, each spring carries a small insulating wedge i,
by which the projections on B alternately lift and e¹. The ends of these
springs are furnished with platinum contact pieces which move between the
four contacts 1, 2, 3, and 4; the spring 1, 1, is connected with the line
by the terminal L, the spring e, e¹, is connected with earth by the
terminal E. The contacts 1 and 2 are in electrical connection with one
another, and with a commutator at Hand H¹ (Figures 2 and 3); the
contacts 3 and 4 are in electrical connection with one another, and with
another part of the commutator J and J. When the key P is depressed
the commutator is in the position shown in Figure 3, and the positive
pole of the battery connected with contacts 1 and 2 by means of the
terminal K, the axis k and arm k¹ of the commutator, and the contact
plate H, which is directly joined to 1 and 2, at the same time the negative
pole of the battery is in connection with contacts 3 and(4 by means of the
terminal Z, the axis s, and the arm &! of the commutator! and the contact
plate J, which is directly joined to the contact pieces 8 and 4. The
depression of the key Praises the detent G, and releases the cam B, which
begins to revolve, while the ratchet a is at the same moment stopped by the
detent G. The two springs and e¹ at first remain both in contact with the
contacts 3 and 4, placing the line and negative pole of the battery in connec-
tion with the earth, while the positive pole is insulated. When the cam has
revolved a sufficient distance to have acquired the full velocity of the
axis A, A', the projection of cam B (Figures 2 and 5) lifts the spring /

page_text: against contact 1, thus putting the positive pole of the battery to the line, and
leaving the negative pole connected with the earth. Thus a positive current
is poured into the line for a fraction of the time of revolution of A, A¹,
depending on the length of the projection x. At the instant that the spring /
falls back to contact 3 ou leaving the projection a, the spring e' is lifted to
contact 2 by the projection y (Figures 2 and 6), and a negative current is
thus poured into the line for a fraction of the time of a revolution of A, A¹,
longer than that occupied by the previous positive current. Asecond positive
current enters the line when the projection & lifts the spring against contact 1
at the moment that e' falls back to 4. A second negative current is sent by
the projection, and a third positive current by the projection v; after this
projection has passed under the wedge i of spring both and e¹ fall back to
contacts 3 and 4, and again place the line in contact with the earth. This
succession of contacts produces a single positive dot at the receiving end of the
cable. If during the revolution of A, A', the key P has been released, the
detent G will fall into the notch g, the cam B will be arrested, the ratchet
released, and no further currents will be sent. If the key be again depressed
the same series of contacts will be repeated, and a second positive signal sent.
If, however, after the completion of the last positive current sent by pro-
jection the key N be depressed the cam will revolve as before, but as the
bar of the commutator will have been moved to J, and the bar z¹ to H¹,
the first, third, and fifth currents which enter the line will now be negative,
and the second and fourth will be positive; this succession of currents will
give a single negative signal. Thus the depression of the keys P and N will
give any succession or combination of positive and negative signals, each
produced by five currents, the relative lengths of which depend on the
projections x, y, z, u, v, of the cam B. The spring or click O is lifted at each
revolution of the cam B by the snail Q, fixed to the cam in such a position
that when the projection has just completed the last current contact for any
signal the spring O drops off the projecting portion of the snail at q, and gives
an audible click, by which the operator is informed that one signal is complete,
and that he may now begin to make a fresh signal. Confusion in the contacts
would arise if the commutator were reversed by a change of keys before this
click were heard.
The instrument shown in the Drawing, when properly adjusted, gives
successive contacts of about the following durations:-+ 100-156 + 80
-32.5+ 26, the signs being such as they would be in making a positive
signal, and after the contacts the cable may be connected with the earth for a
short time before another signal is given; this the instrument it will be

page_text: observed is arranged to do. These contacts are well adapted for a line
similar to the Atlantic cable as now constructed. It is intended that the
resulting current or shock arriving at the further end of the cable in conse-
quence of each succession of contacts should be of a maximum strength of
somewhat less than one per cent. or more of the current which the battery
employed in working the telegraph would be able to maintain through the
cable were it connected with it for an indefinite time. The speed at which
the axle A should be driven will be from 100 to 120 revolutions per minute,
but the best speed can be found by experiment, and will be that at which the
currents or shocks obtained at the further end are somewhat less than one
per cent. of the current the battery is able to produce, as before mentioned.
In order to enable an electrician to adapt the contacts to the requirements
of different cables and instruments, the following information will be found
useful-It will be necessary for him first to determine according to his
judgment what proportional strength the working shocks or currents should
bear to the current which the battery employed would be able to cause to
pass through the cable if connected with it for a considerable time; this
proportion will depend principally on the receiving instrument; for long and
slow lines very sensitive receiving instruments will usually be employed, and
the proportional strength of the currents or shocks will be very small, whilst
for shorter and quicker lines the receiving instruments do not require to be
so sensitive, and the proportional strength of the currents or shocks to work
them will have to be greater. If the electrician determine that about a one
per cent. current or shock is necessary he may use the contacts of the
instrument shown in the Drawings, and he will adjust the working speed of
the machine until he finds by experiment that about one per cent. currents
or shocks are obtained. If a five per cent. current or shock is desired the con-
acts may be as follows:- +0.7-1.14 +0.7-0.26 + 0.00; with this
combination no earth connection is theoretically necessary, so that the total
duration of the signal will be 2.86; or a five per cent current may be obtained
with three contacts, thus:- +07-105 +0.4; earth contact 1.0; total
duration, 3.15; or +0.63 0.83 + 0.27; earth contact 1·5; total
duration 3.23 (this last is somewhat less than a five per cent. signal). The
unit of time is the same in each of these signals (with the exception of the
one per cent. signal), so that the advantage in speed obtained by using five
contacts in place of three is evident. For a twenty per cent. current or shock
the contacts may be (in the same units) +.152-1.76 +0.66; with this
combination no earth contact is necessary, and the total duration is 3.94
units. The actual working speed of the machine will in each case be adapted

page_text: by experiment to the line to be worked, as already explained. One or other
of the examples above given will be found to suit approximately any ordinary
long telegraphic cable, but in some cases the electrician may be able to make
a nearer approximation to the requirements of a particular case by observing
that as the strength of the current or shock required becomes less (as com-
pared with the current the battery is able to pass through the cable) so the
total duration of the positive and negative contacts becomes more nearly equal.
If it be desired to produce at the distant end of the line, in addition to short
signals such as already described, signals of some duration corresponding with,
say a line in Morse's alphabet, it may be done on the same principle by
increasing the duration of the several currents, and somewhat altering their
proportions; thus an indicationofgreaterstrengthand somewhat longerduration
is obtained; for example, a 20 per cent. contact may be used for the long signals,
whilst five per cent. contacts are employed for the short and small signals; or
without increasing the strength of the indication its duration may be prolonged
by introducing a series of rapidly alternating currents so proportioned as to
maintain the current at the distant end of the strength required; this, however,
is not usually so convenient. Thus it will be seen that a transmitting instrument
may be constructed to send into a telegraphic line combined currents, as above
described, suitable to give at the further end of the line four distinct signals;
viz., 1, a feeble signal of short duration and positive sign; 2, a similar signal
of negative sign; 3, a signal of greater strength or duration, or both, and of
positive sign; and, 4, a signal similar to that last mentioned, and negative in
sign. Similarly an instrument may be made to give combined currents for
signals of three or even a greater number of different strengths or durations.
Also, if it is desired, the strength of the signals may be varied by varying the
battery power; for example,in an instrument such as is shown in the Drawing
four keys may be combined with one cam, two keys working with the feeble
power, and giving positive and negative signals respectively, and the other
two keys working similarly with the stronger battery power. If it is desired
to work with an alphabet on the Morse principle two keys are employed, one
key releases a cam which produces a dot; the other key releases another cam
which produces a dash, and in this case, and generally when it is desired to
give signals of different durations, the cams should be on different axes, with
different speeds of rotation, or some equivalent arrangement should be resorted
to, such, for example, as making the shorter cam to do its work in half a
revolution of the axis, whilst the longer cam takes a whole revolution; the
shorter cam may in this case be made double to avoid loss of time. In place
of arranging the cams to travel intermittently they may be kept revolving

page_text: continuously, but without sending currents into the telegraphic line until tne
key is depressed, and the apparatus connected with the key is so arranged
that at whatever time during the rotation of the axis the key is put down it
commences to act ouly at the starting point of the cam, and continues to act
until all the currents required for the signal have been sent into the line; the
arrangement described is, however, preferred. Or the cams may act con-
tinuously on their springs or levers, and then the key acts to put the springs
or levers belonging to its cam into the telegraphic circuit at the commencement
of the signal, and to take them out at the end thereof; or the springs or levers
may be kept out of contact with the cams, except when their keys are
depressed; these methods, however, are not superior to that which is described
in detail. If desired the cams may be so constructed as each to send into the
line combined currents suitable to produce two or more currents at the distant
station, for instance, so as to indicate a particular letter corresponding with
the key employed. Also in place of cams it is evident that cylinders to receive
moveable type-like projections may be employed, or type may be assembled
on a flat surface having a motion given to it at a suitable speed to carry the
type under springs or levers such as those on which the cams are described to
act. Each type will have several projections on it suitable for sending into the
telegraphic line combined currents such as to produce either one, two, or several
currents at the distant end of the line.
We would remark that in the Specification of a former Patent granted to
one of us, viz., to the aforesaid William Thomson, bearing date the 20th
February 1858 (No. 529), there is described methods of producing signals
through a long submarine telegraphicline, which are to some extent analogous
to those herein-before described. According to one of these methods a signal
was produced by sending into the line wire for a given time, say for one
second, a current of a certain strength (call it 48), then for another second
there was sent into the line wirea current of opposite sign of greaterstrength,
say 50, and, lastly, for a third second there was sent into the wire a current
of the same sign as the first, with a strength of, say, 12. In this way the
result required was approximately obtained, but the method is inconvenient,
requiring, as it does, the use of three different strengths of electricity; besides
which, the use of the weaker current involves a loss of time.
There is also a simpler arrangement described in the same Specification; it
consists in sending first a current of the same sign as that which is intended
to arrive at the further end of the line, and then another current of opposite
signand the same strength, but continued forashorter time, so as to neutralize
the excess of the first current. This method is simple, and to some extent

page_text: accomplishes its object, but it will not give a speed equal to that given by the
method herein-before described, where the duration of the second current
exceeds that required to neutralize the excess of the first and a subsequent
compensation is made by the use of another current or currents.
We would further remark that three is the greatest number of currents
ever heretofore employed to produce a single indication, and that with very
slow cables a much better effect is obtained by employing according to our
Invention apparatus for sending into the telegraphic line four, five, or a greater
number of currents to produce a single indication.
It is obvious that although not so convenient it is possible to use four or a
greater number of currents or shocks of unequal strength to produce a single
indication, and the information given in this Specification will enable an
electrician properly to proportion the durations of such currents or shocks, as
it will be necessary only to follow the directions already given, with the
exception of making suitable allowance for the strength of the currents or
shocks which he is employing; these proportions can also be adjusted by
experiment.
What we claim is,―
First, the arranging telegraphic apparatus to send automatically into the
circuit in rapid succession three or a greater number of currents or shocks of
equal strength and properly proportioned, as described, to produce at the
receiving end a single current or shock.
Second, we claim the arranging telegraphic apparatus to send automatically
into the circuit four or a greater number of currents or shocks (of equal or
unequal strengths), properly proportioned as described to produce at the
receiving end a single current or shock.
Thirdly, we claim the arranging apparatus for transmitting electric currents
into a telegraphic circuit, as herein-before described.
In witness whereof, I, the said Cromwell Fleetwood Varley, have
hereunto set my hand and seal, this Fifth day of January, in the year
of our Lord One thousand eight hundred and sixty-six.
CROMWELL F. VARLEY. (L.S.)