IMPROVEMENTS IN SHIPS' COM- PASSES, AND IN THE MEANS FOR CORRECTING THE DEVIATIONS THEREOF
Year: 1878

page_text: LETTERS PATENT to Charles Denton Abel, of Southampton Buildings, in the
County of Middlesex, for the Invention of IMPROVEMENTS IN SHIPS' COM-
PASSES, AND IN THE MEANS FOR CORRECTING THE DEVIATIONS THEREOF.”
A communication from abroad by Josef Peichl, Lieutenant of the Austrian
Navy, at present of Pola, in the Austrian Empire.
Sealed the 11th March 1879, and dated the 21st September '1878.
"
PROVISIONAL SPECIFICATION left by the said Charles Denton Abel at the
Office of the Commissioners of Patents on the 21st September 1878.
CHARLES DENTON ABEL, of Southampton Buildings, in the County of Middlesex.
IMPROVEMENTS IN SHIPS' COMPASSES, AND IN THE MEANS FOR CORRECTING THE
DEVIATIONS THEREOF." [A communication from abroad by Josef Peichl, Lieutenant
of the Austrian Navy, at present of Pola, in the Austrian Empire.]
This Invention has for its object, firstly, to greatly increase the mean directive
force of ships' compasses by the application thereto, in a manner to be presently
described, of relatively small masses of soft iron free from permanent magnetism,
without thereby affecting the deviations resulting from the locality where the
compass is placed; secondly, according to this Invention, such intensifying
apparatus may be applied by a peculiar arrangement of the iron masses to accurately
compensate or correct the quadrantal deviations of the compass, and also under
certain conditions, the heeling error thereof to a certain extent, so that by employing
in combination with the above means the ordinary well-known means for com-
pensating the semicircular deviations, the compass may be made to indicate with
accuracy and with a hitherto unattainable sensitiveness the correct magnetic course
of the ship.
The intensifying apparatus in its simple form consists of a number of soft pure
iron bars of any desired section, and of equal size and inductive capacity arranged
Posice 8d1

page_text: radially round the compass bowl in such a manner that they lie in a plane forming
the continuation of that of the compass card, and that they all radiate from the
centre on which the compass card swings. The bars are all at equal distances
apart, and are also equidistant from the centre of the whole system. They are
carried by a framing of copper or brass which is suspended in the gimbal ring in
order to maintain the bars horizontal during the rolling and pitching of the ship.
The apparatus is situated either in a hemispherical enlargement of the binnacle
with hemispherical cover, or in any other enclosure suitable to the locality where
it is applied. The number, form, and size of the bars may vary within certain
limits; 16 larger or 32 smaller ones have been found to answer best. In place of
bars, soft iron balls might be employed. The compass cards most suitable for use
with this apparatus are those with four magnet needles or four pairs of such.
The framing is grooved to receive the bars which are so arranged that two are
always diametrically opposite each other. The inner ends of the bars are situated
about 23 to 30 millimetres (89 to 11 inches) from the ends of the compass needles,
and thus become very considerably induced thereby, such reaction establishing an
essential difference between the present Invention and Airy's method of mechanical
correction by means of soft iron. This difference is further proved by the fact that
in the present compensating method by means of soft iron based on Poisson's
fundamental law, the deflecting forces of those two of such iron correctors neutralise
each other, which are situated at right angles to each other, their dimensions and
distances from the centre being equal, whereas with the present apparatus the
deflecting forces of those two of the bars are in equilibrio, which in the complete
radial system are arranged respectively symmetrically in relation to the four
cardinal points north, east, south, and west. The above-described intensifying
apparatus is at the same time rendered applicable for correcting the deviation of
the compass in the following manner: Firstly, the semicircular deviations is
compensated according to Airy's method, but so that the respective correctors are
freed from the rolling and pitching motion by suspension in the gimbal ring. The
apparatus is for this purpose provided with a vertical brass rod situated below the
compass in its vertical axis, and carries adjustible magnetic bars. If the deviation
be so great that the said magnets are not sufficient for entirely neutralising the
same, one part thereof is neutralised in the usual manner by fixed magnetic bars,
and the remainder by the magnets of the apparatus which must be adjusted to
correspond with changes of deviation due to different latitudes or other causes if the
compass is to be maintained magnetically correct; secondly, the quadrantal
deviation is compensated completely, and with the greatest precision by the before-
described intensifying bars themselves, without the use of special masses of iron.
For this purpose, instead of making the bars all of equal section and length, bars of
equal section but of unequal length are used, and instead of their ends all being
equidistant from the centre, they are arranged at unequal distances. Thus, assuming
16 radial bars to be arranged so that No. 1 points to the bows of the vessel, No. 9
to the stern, and Nos. 5 and 13 respectively to starboard and port, while the bars
bearing the other numbers are arranged in consecutive order and symmetrically at
intermediate positions; then the bars Nos. 3, 7, 11, and 15 have the normal length
for the bars of the simple intensifying apparatus previously described, and they are
also situated at the normal distances from the centre. The bars 16, 1, 2, 8, 9, 10,
are of equal length, but shorter than those above mentioned, while their distances
from the centre are also equal to one another, but greater than those above
mentioned. On the other hand, the bars 4, 5, 6, 12, 13, 14, are equal, but of greater
length than 3, 7, 11, 15, and their distance from the centre is less than these. The
simple intensifyer can also be converted into a compensator if the distances of the
bars from the centre of the compass are regulated according to the just described
system, and the correctors for the semicircular deviations are employed.
For simplifying the compensating operation, the arrangement may be adopted of
inounting certain of the bars on slides that can be adjusted to graduated scales on

page_text: the framing; thus referring to the above enumeration of the 16 bar arrangement,
the bars 16, 1, 2, lying towards the bows are mounted on one slide, those 4, 5, 6, to
starboard on another, &c., while 3, 7, 11, and 15, are fixed.
Third. The heeling error can in certain cases be corrected by the intensifying
apparatus if this be so arranged that the one axis of the framing is not mounted in
the gimbal ring of the compass, but directly in opposite bearings in the compass
casing, so that the apparatus is made to partake of the rolling motion of the ship,
but is freed from the pitching motion. In this case the compass bowl is provided
with two pivots in the direction of the keel carried in bearings on the framing of
the intensifying bars, so that the compass bowl alone is freed from the rolling
motion, and from the pitching motion conjointly with the apparatus.
The vertical force of the permanent ship's magnetism is neutralised in the usual
way by an adjustible vertical magnet on a vertical brass rod fixed on the compass
casing, which rod may at the same time carry the correctors for the semicircular
deviations.

page_text: The entire system whether employed by itself or in combination with the other
means of correction is mounted within the gimbal ring of the compass and is enclosed
in a hemispherically enlarged compass box with hemispherical cover, or in an
enclosure suited for the particular locality where it is applied. The number, form,
and size of the bars of the multiplier is variable within certain limits, but these
factors have a considerable influence on the effectiveness of the system of bars which
is moreover dependent on the number, description, and size of the compass needles..
According to present experience it would appear best to apply a multiplier
consisting either of 16 bars (Figure 1) of about 20 centimeters (7·8 ins.) in length,
with a cross section of 4 square centimeters (0.5 square inches), or of 32 shorter bars
12 centimeters (4-6 ins.) long and about one square centimeter (0·14 square inches)
section. The number of bars can however be increased until the inner ends abutt
against each other so as to form a closed ring or massive soft iron plates, or such
built up of parallel bars may be employed as shewn at Figure 2, or annealed balls
as at Figure 3 may be combined to form the multiplier.
Also the essential feature of the system shown at Figure 1 will not be altered if all
the bars are inclined at an equal acute angle to the horizontal plane of the compass
card, so that the inner ends remain in this plane while the outer ends are all either
above or below it.
The compass cards in present use most suitable for the above purpose are those
with four needles or pairs of needles of the dimensions of the English regulation
compass card, which may be either applied to an ordinary or to a fluid compass.
The before-mentioned distance existing between the ends of the needles and the
inner ends of the bars shows directly the essential difference between the intensity
multiplier and Airy's method of mechanical correction with soft iron. A bar only
from 20 to 40 millimeters distant from a magnet needle will clearly be considerably
induced thereby, and even in the contiguous bars magnetism will be produced, the
re-action of which on the system of magnets will be appreciable..
This essential difference is furthermore shewn in this that with Airy's correction -
with soft iron the deflecting forces of each two correcting bars counterbalance each
other if with equal dimensions and at equal distances from the centre c of the
compass they are place at right angles to each other, whereas with the multiplier
the deflecting forces of those bars, &c., counterbalance each other, which, in the
complete radial system are arranged respectively symmetrically in relation to the
four cardinal points, north, east, south, and west.
In other words the deflecting forces of Airy's correctors of soft iron obey the
law sinus 2 azimuth, while those of the multiplier bars obey a law differing con-
siderably from the above.
b. The application of the intensity multiplier also as corrector of deviations.
1. If the system of bars represented diagramatically at Figure 1 be placed on
board vessel so that bar No. 1 lies in the direction of the keel ahead of the centre c
of the compass, and the system be inclined for instance on the transverse axial line
13-5 to a constant acute angle without bringing the compass bowl out of its
normal position the system of bars at the same time that it increases the mean
directive force produces also a semicircular and a quadrantal deviation. If the ship
is situated in the northern hemisphere and the system be so inclined that the bars
14, 15,.... 4 lie above the horizontal plane of the compass card, the resulting
semicircular deviation obeys the same laws as those which are produced by a
vertical iron bar of the type - c (Admiralty manual).
If the said bars lie under the said plane the system possesses a deflecting force
+c, the quadrantal deviation which is produced in both cases is negative.
2. If the system be inclined in a similar manner to that above described, but in
the direction of the longitudinal axis 1-9, it will have a semicircular deflective
force + (Admiralty manual), and the quadrantal deviation produced in this case
is positive.
3
3. If the system be inclined on an axis situated between 1-9 and 13-5 it will

page_text: have semicircular deflective forces +c and +f, and will produce quadrantal devia-
tions +D and +E.
4. If the system is not permanently inclined but is so mounted in the compass
box that it is rendered independent, by the gimbal rings, of the pitching motion of
the vessel but not of the rolling motion, and consequently partakes of this motion,
whereas the compass bowl which is supported in pivots in the direction of the keel
remains in the normal position; in this case the system of bars corrects the one
part of the heeling error.
5. If the system of bars be fixed in the compass box so that only the compass
bowl is suspended in the gimbals and a vertical soft iron cylinder be mounted per-
pendicularly over the centre c of the compass, or in lieu of a cylinder a number
of soft iron bars arranged in cylindrical form, such a system will operate as a simple
multiplier.
6. If the bars of the system shewn in Figure 1 are not mounted concentric to the
compass centre, but so that the curve drawn through the inner ends of the bars
forms an ellipse, of which the long axis lies in the direction of the keel 1-9 while
the conjugate axis lies in the transverse direction 13-5, such a system lying hori-
zontally in the gimbals will produce a quadrantal deviation -D.
7. If the long axis of the above-described ellipse lie in the transverse direction
13-5 the system will produce a quadrantal deviation + D.
8. If the long axis of the ellipse lie for instance in the direction 2-10
(forming with the keel direction an angle of two points) the system will produce a
quadrantal deviation of -D and -E.
9. If the long axis lie in the direction 16-8, the system will again produce a
deviation D but a + E.
10. If the two systems of equal dimensions described under 8 and 9 be combined
into one, being placed one above the other, and this be so mounted on the compass
bowl that the plane of contact of the two systems coincides with the horizontal
plane of the compass card the combined system will produce a - D, and the
deviations E produced by the two halves of the system will counterbalance each
other.
11. If the long axis of the ellipse of the one half of the system described under
10 lie in the direction 3-11, and the analagous axis of the second half in the
direction 157, the whole combined system if suspended in the gimbals will
operate as a simple multiplier, producing neither a deviation D nor a deviation E.
12. If the combined system described under 11 is applied as under Nos. 1 to 5 it
operates just the same as the simple system of bars there described.
13. If the combined system described under No. be employed, and if in addition
the bars are made of different lengths in such a manner that in 1 and 9 are the
shortest, that 2, 8, 10, 16 are longer but equal to each other, that 3, 7, 11, 15 are
still longer and equal, that 4, 6, 12, 14 are still longer and equal, and that 5-13, are
the longest, the quadrantal deflecting power of the system will be very considerably
increased.
14. This power of the system can be still further increased if the cross sections
of the bars are gradually increased from the direction of the keel towards the
transverse direction in such manner that the bars of the smallest section lie in the
direction 19, while those of the greatest section lie in the direction 13-5.
15. With the ball system balls of varying diameter are applied in an analagous
manner, namely, 1-9, being the smallest, 2, 8, 10, 16, somewhat larger and equal,
3, 7, 11, 15, still larger and equal, 4, 6, 12, 14, still larger and equal, and 5, 13, the
largest.
F
16. If only one half the intensity multiplier be applied to the compass; for
instance, only the bars 1, 2, 3, 4, 5, 6, 7, 8, 9 (Figure 1), placed exactly as shown in
this Figure, this half system will in the horizontal position produce a regular
quadrantal deviation D, and will at the same time increase the mean directive
force.

page_text: 17. The bars 2 to inclusive 10 alone applied as multiplier will produce quadrantal
deviations D and E, and increase the mean directive force.
18. If the bars of one half of the multiplier be inclined until they are vertical,
such that their inner ends retain the same distance from the ends of the needles of
the compass card, as shown in Figure 1, they produce as one half of the entire
system a regular semicircular deviation.
19. If the one half of a simple multiplier be fixed to the upper turn plate S₁
(Figures 5 and 6) while the other half is fixed to the lower turn plate S₁, then if
the nut O of the D mechanism is moved towards the compass bowl, that is, if the
two turn plates are not turned in contrary directions, these halves will form a
simple multiplier, but if the plates are turned in contrary directions from each other
the duplex system consisting of two half multipliers will form an intensity multiplier
and a quadrantal corrector in an analogous manner to the elliptical systems in
Figures 5 and 6.
c, Airy's correction of the semicircular deviation.
This correction is with the universal corrector applied directly to the compass,
and is consequently entirely freed by the gimbal rings from the rolling and pitching
motions of the ship.
The correctors are adjusted and fixed by a mechanism shown at Figure 6, whereby
their adjustment is simplified.
d, combined use of the multiplier and quadrantal corrector with Airy's correction
with soft iron bodies; new application of the last-named correctors.
The corrections of the quadrantal deviations described under No. 6 to inclusive
15 of section I. is not perfectly accurate for all geographical latitudes. A small
fraction of the compensated deviation will appear again in considerable alterations
of latitude, and the adjustment of the respective correctors will then have to be
rectified; this is effected,-
a. In the case of a single system of bars or balls, either by a re-adjustment of the
bars or balls in an ellipse with larger or smaller axial difference; or by the use of
this system with fixed bars and with Airy's correctors of soft iron applied in a new
and peculiar manner.
B. In the case of the double system of bars, shown at Figures 5 and 6 by a cor-
responding adjustment of the respective mechanisms.
The new application of Airy's correctors referred to in the second section of a is
shown in the diagram at Figure 4 at the same level with the horizontal plane of
the compass card, and concentric with the centre c of the compass, two brass rings
are fitted round the outside of the compass box so as to be rotatable round the
same. To facilitate their uniform rotation in rotary directions they may be
formed as toothed wheels, having between them a small pinion in geal therewith.
Each ring bas at two diametrically opposite points of its outer circumference a
receiver for holding a ball or cylinder of soft iron. The dimensions and inductive
capacity of all the balls are equal.
The receivers are so constructed that the centre of each ball shall lie in the
horizontal plane of the compass card. The two rings with the pairs of balls a, a',
b, b', can be fixed in any position by means of suitable clamping arrangements. On
the outer surface of the compass box may be provided a graduated scale for marking
these positions.
The pair of balls or cylinders operate in certain positions (relative to the cardinal
points x, x, y, y', and to the intercardinal positions u, u, v, v¹, of the ship (and
which in the case of balls I will designate by the positions of the rear balls only) as
follows:-
1. In the symetrical positions a¹, b, (intercardinal directions) the mean directive
force is increased without producing diviations.

page_text: t
2. In the symetrical positions a,1, 6, they produce a maximum deviation-D in
α₁₂³, b₁, an equal maximum deviation + D.
3. In a, b, they produce a -D lying between zero and the maximum deviation;
in a, b, an equal deviation + D.
4. By all possible symmetrical adjustments between the positions a¹, b, and a₁¹,
or a, b, and a, b, all deviations + D, lying between zero and the maximum pro-
duced in a, b, can be produced without altering (as in Airy's mode of application)
the distances of the balls from the compass centre; but if both rings are turned in
the same direction until for instance the pair of balls a₁, b₁, touching each other are
either in a position between a₁, b₁, and a₁, or between a₁, b₁, and b₁, and the rings
are then fixed, then the balls will produce quadrantal deviations + Dand + E.
If the intensity multiplier and deviation corrector have been fixed in position for
the quadrantal deviation corresponding to the locality where the adjustment is
effected, and the four balls are fixed in the positions a, a, b, b', the fraction of the
quadrantal deviation corrected by the multiplier, which appears in changes of
latitude, can be corrected by the above-described method by means of the system
of balls.
Even with a single ball on each ring, or if the receivers of these single balls are
only shifted horizontally in guides, or upon a graduated ring outside the compass
box in the sense of the above points Nos. 1 to 4, and are then fixed, the above
purpose may be accomplished.
The guides of the receivers must in this case be so arranged that the balls can be
moved horizontally from the positions a, b, (Figure 4) to the positions a, b, and
in such manner that the one ball moves in the starboard semicircle a₁, α, b₁, b₁, and
the other in the port semicircle b₂', b¹, a', a₂'.
The combined application of this system and of the multiplier allows of a con-
siderable reduction in the length of the iron bars, and consequently in the diameter
of the compass box. But if the double system of bars above referred to under ẞ be
employed the use of the brass rings with the system of balls is dispensed with.

page_text: the bowl, and having a radial slide n in the radial groove of which the nut o can be
adjusted by the screw p if the latter be turned by a key inserted at D.
The slide n is fixed to the concentrically slotted frame q by means of two
pinching screws E, and can be moved laterally in the slot of q by the key at D on
relieving the screws E.
The nut o has two curved rods r, r¹, connected to it, of which is connected to
the star-shaped plates which is rotatable, concentrically round the bowl b over
the ring m, and is connected by angle pieces t with the disc s'.
This disc is rotatable concentrically round the compass bowl and carries the
intensity multiplier and quadrantal corrector in such a manner that the lower sides of
the iron bars are situated somewhat above the horizontal plane of the compass card.
. Under this system of bars and immediately above the star-shaped plate's is a
similar plate S with a similar system of bars. This plate being broken away in
Figure 5 the arrangement of these bars in form of an elipse is shewn more clearly
(1, 2,. . . . 9, are the bars of the first quadrant). To the plate S the rod ris
directly connected by means of a vertical pin passing through a slot in the inter-
mediate plate 8.
If the screw p be turned so that the nut o is for instance shifted towards the
end D, the two systems of bars are turned equally in contrary.directions, and such.
motion can be continued until, for instance, the bars 1 of each system are at right
angles to each other. When adjusted to this position the two systems constitute
together a simple intensity multiplier.
If the nut o be shifted towards the compass bowl a gradually increasing deflecting.
force of the double system of bars will be developed, and if this be continued until:
the bars 1 of both systems are accurately one above the other, the double system
will have the maximum quadrantal deflecting power.
If the D mechanism be adjusted for a certain value of D, and the slide be moved.
(after relieving the screws E) in such manner that as shewn in Figure 5, it is.
inclined to the connecting line of the transverse axes g; the double system will
produce quadrantal deviations D and E. Figure 6 shews the arrangement of the
apparatus in the hemispherically enlarged compass box, as also the correction of
the heeling error according to the generally adopted method by means of a vertical
magnet y.
By means of an endless chain this magnet can be adjusted to any height and
fixed by the clamping screw K.
The illumination of the compass card is effected by means of a lamp in the top
of the hemispherical cover to the compass box not shown on the Drawing.
In the aft side of the compass box shewn in Figure 6 a door with lock is pro-
vided through which the screws A, B, C, D, E, can be reached by the hand. The
clamping screw K is reached either through a special opening in the lower part of
the box, or it can be arranged in the hemispherical part of the box.
IV. SPECIAL ARRANGEMENT OF FLUID COMPASS WITH THE UNIVERSAL
COMPENSATION.
In order to prevent the vibrations of the compass card the construction of fluid
compass is employed shewn in section at Figure 7. Figure 8 shews the flat part
of the stopping motion, and Figure 9 shews to a smaller scale the lower plate cl
which carries the B and C mechanism together with the plate of the caoutchouc
bag lying over it. The compass card may be of any suitable construction such as
the regulation form.
This compass is so constructed that it can be inserted in the place of the ordinary
compass bowl in the universal compensation apparatus shewn at Figure 6, without
in any way altering that apparatus.
a is any suitable fluid compass card either according to the four needle system
or with Duchemin's steel rings, and it may have metal chambers placed between
the needles I., II., III., IV., as floats.. b is the compass bowl to the outer surface of

page_text: which is applied the D and E mechanism of the universal compensation. 6" is a
chamber fixed to the bowl b above the said mechanisms and communicating with
the interior of the bowl, and containing the stopping device; a, &, is the glass
cover; o, an opening in the middle of the bottom plate 61. B is a caoutchouc bag,
the neck of which is passed through the hole o and is pressed by the base of the
column S against the inner surface of the plate b¹, so that the opening o is made
water-tight, only allowing of the communication o¹, o¹¹, between the bag B and the
bowl b; c is the star-shaped base plate of the universal compensation corresponding
to c, Figures 5 and 6; c¹ is a metal box in place of the truncated cone i (Figure 6),
and containing the caoutchouc bag B, the plate supporting which is adjusted up or
down by means of screws F on which are nuts Z attached to the plate. To the
plate o are fixed the B and C mechanism.
The setting screws A pass through the base c and screw into metal blocks soldered
to the base b₁ of the bowl so as to secure the latter.
The rim of the glass cover of the compass is secured to the top rim of the bowl
by screws S, and is rendered water-tight by a caoutchouc packing between the
two.
The glass is so let into its rim that the under sides of both are flush, so that
any air bubbles that may collect can escape into the channel i formed round the
rim which has at j a small air valve communicating with the channel i.
The stop mechanism consists of a cylinder a, lever a¹, the slide a", curved to
the side of the compass bowl, the continuation all of this slide in the chamber 611
and the screw device a¹. The space of a chamber is only of a size requisite for
the parts of the stop mechanism contained therein. Figure 7 shews the compass with
expanded bag, in which case one portion of the liquid (dilute alcohol, &c.) has passed 2
from the bowl into the bag, so that the liquid in the bowl has sunk below the
chamber 6. If the cover is now screwed off and the stop mechanism a be raised the
card point and agate can be changed. If the cover be closed again and the bag ẞ be
compressed by means of the screws F, the valve j being open the liquid will rise in
the bowl until it enters the channel i. If the stop mechanism be now lowered 3
again the compass will be in working order.
If the bag be made larger so that it can contain the whole quantity of the
liquid the compass can be used, both as a fluid compass and as an ordinary one.
The bag has also for its object to take up that portion of the liquid which is
forced out of the bowl through the openings o', o", through expansion due to 3
increase of temperature, it being made of sufficient elastic material for this
purpose.

page_text: will be obtained Airy's correction of quadrantal deviations applied in a new
manner and combined with the multiplier.
4. It will be evident that correctors B and C of the semicircular deviation may
for example be attached to the support for the vertical magnet y, in which case
the multiplier will be in combination with the usual correction of the semicircular
deviation.
Having thus described the nature of the said Invention and in what manner the
same is to be performed, as communicated to me by my foreign correspondent, I
claim,―
First. The method of increasing the mean directive force of every description of
compasses, whether ordinary or fluid compasses, by means of a system of bars,
plates, or balls, arranged and operating as an "intensity multiplier," substantially
as herein described.
Second. The use of the "intensity multiplier" as a corrector of deviations
according to the various modifications herein described.
Third. The application of the intensity multiplier with or without the corrector
of deviations within the gimbal rings, whereby these means of correction are freed
from the rolling and pitching motion of the ship.
Fourth. The before-described new arrangement of balls or cylinders of soft iron
applied to the outer circumference of the compass box as corrector for all quad-
rantal deviations between zero and the maximum amount, without altering the
distance of these means of correction from the centre of the compass.
Fifth. The use of a duplex system of iron bars, plates, or balls as intensity
multiplier and corrector of quadrantal deviations, as also the respective mechanisms
employed for this purpose herein described, and shewn in Figures 5 and 6 of the
Drawings.
Sixth. The use of one half of the simple intensity multiplier for increasing the
mean directive force and correcting the quadrantal deviations, or for correcting the
semicircular deviations as herein-before stated under the heads 16, 17, 18.
Seventh. The use of a duplex system of semi-multipliers, as herein described
under the head No. 19.
In witness whereof, I, the said Charles Denton Abel, have hereunto set my
hand and seal, this Twentieth day of March, in the year of our Lord One
thousand eight hundred and seventy-nine.
CHAP. D. ABEL. (L.S.)