MARINE, FORT, AND FIELD ARTILLERY
Year: 1806

page_text: LOGANS SPE
ATION.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I,
MICHAEL LOGAN, of Paradise Street, in the Parish of. Rotherhithe, in
the County of Surrey, Engineer, send greeting.
WHEREAS His present most Excellent Majesty King George the
Third, did, by His Royal Letters Patent, under the Great Seal of the
United Kingdom of Great Britain and Ireland, bearing date at West-
minster, the Thirteenth day of March, in the forty-sixth year of the
reign, give and grant unto me, the said Michael Logan, my executers,
administrators, and assigns, His especial license, full power, sole privilege,
and authority, that I, the said Michael Logan, my executors, adminis-
trators, and assigns, during the term of years therein expressed should
and lawfully might make, use, exercise, and vend, within England,
Wales, and the Town of Berwick upon Tweed, my newly invented
system of "MARINE, FORT, AND FIELD ARTILLERY," in such manner, as
to me, the Michael Logan, my executors, administrators, and assigns,
should in our discretion seem meet, in which said Letters Patent is con-
tained a proviso, that if I, the said Michael Logan, should not particu-
larly describe and ascertain the nature of my said Invention, and in
what manner the same is to be performed, by an instrument in writing

page_text: under my hand and seal, and cause the same to be inrolled in His
Majesty's High Court of Chancery within one calendar month next
and immediately after the date of the said Letters Patent, that then
the said Letters patent, and all liberties and advantages whatsoever
thereby granted, should utterly cease, determine, and become void, as
in and by the said recited Letters Patent, relation being thereunto had,
may more fully and at large appear.
NOW KNOW YE, that in compliance with the said proviso contained
in the said Letters Patent, I do, the said Michael Logan, do hereby
declare that my said Invention of the new system of construction and
the principles of operation produced in the practice and management
of the above mentioned marine, fort, and field artillery is ascertained
and described conformable to the following maxims and explanations
herein and hereafter expressed, that is to say: First, the cannon or
gun carriage is reduced by construction to occupy the least possible
space, and consequently to present the least surface to the action of
either the direct, oblique, or flauk fire of the enemy. Secondly, for the
security of the gun carriage in time of action, when employed for sea
service on board of line of battle ships or other ships of war, or
ns marine or fort artillery, it is covered from the fire of the enemy by
the gun and fulcrum, and is by construction rendered permanent and
always true to the centre of the port or embrasure. Thirdly, the recoil
or reaction of either light or heavy cannon is, by the operations of this
system, completely performed within the carriage itself and can be
diminished or increased at pleasure. Fourthly, the horizontal range
and the clevation or depression of cannon in the time of action is
correctly performed with an uniform motion, and with the greatest
facility and security to those employed in the operations of this artillery.
Fifthly, the cannon or gun carriage containing in itself by the geomet-
rical design of its construction the least quantity of of materials of which
it can be made, and the strongest fortification against the effects of either
Lot or hells. It is, therefore, my intention to render its system, or
the same artillery, at once subservient and universally applicable and
convenient, with the utmost dispatch, to the three great operations of
national warfare. that is for either marine, fort, or field service. Having

page_text: thus specified five of the principal maxims observed in the construction
and effectually performed in the practice of this artillery, I here give
only such descriptions and explanations of the nature of my said In-
vention as are consistent with my duty in the promotion of public
security, and the designs or proper objects of military mechanics. The
system, therefore, of construction in mounting either light or heavy
cannon for marine or fort service will be found to consist in the follow-
ing parts, that is to say; First, the body of the cannon or gun carriage.
This may be made of wood, iron, composition of metal, or other fit
material. Secondly, the fulcrum which I make either of cast iron or
composition or other fit material, and which supports the piece of
ordnance or cannon by its trunnions upon the carriage, either by a single
cylinder or by two parallel cylinders in a horizontal position upon iron
axles. Thirdly, the train bar and cylinder with the gun screws and bed
of cascable, which in time of action, elevate or depress the breech of the
cannon, or in other words, determine the position of the gun's axis to
the plane of the horizon. Fourthly, the recoil chain with its fore roller,
chain, staple, and butt pinion fixed on iron axles in the front and butt
of the carriage. Fifthly, the bolster or head bearing, and the legs
which are united and combined in construction by the tie or span iron,
parallel to the base of the carriage. Sixthly, the centre pin and fore
staple which is fixed by strong bolts to the lower sill of the port or
embrasure. Seventhly, the train post. and swifter by which one man
only is enabled to give the heaviest artillery or piece of ordnance its
horizontal range with a steady uniform motion, and to sustain it with
the greatest ease in any assigned position, either upon the deck of a
line of battle ship or other ship of war, or on the platform of a battery
in time of action. In my exemplifications of those parts in construc-
tion, I here limit myself to the specification of the system as applied
to the piece of heavy ordnance already proved and established by
experimental practice, being a thirty-two pounder 10 feet, 7 inches,
4 lines, in length; 21 inches, 9 lines, diameter, in the breech; and
weighing 6328 lbs. avoirdupois. The body of the carriage for this piece
of ordnance I have made, and consists of but one solid piece of elm
containing but 13-5 cubic feet of timber. Its form, in the vertical

page_text: plane or section, being a variable figure consisting of a right line and
a curve, the curve rising from the right line to the level of the gun's
axis in the plane of the horizon, and its place being a parallelogram
terminated at each end or at the front and butt of the carriage by semi-
circular arches. In its dimensions, its length from front to butt upon
the base line being equal to that of the cannon's, its extreme breadth
equal to the diameter of the breech, and its thickness to that of the
anetal under the chamber at the breech. From the centre of the front or
guard plate of the carriage to the point of contact with the curve, I
have denominated the chase level or plane of the carriage, and from
this point of contact (called the train point) to the centre of the butt
I have named the train of the carriage. This distinction of parts of
the body of the carriage I have found necessary as being directly
connected with the operations and effects of the artillery in action. From
the diameter of the front arch to that of the butt, in the middle of the
plane and base of the carriage, is cut a regular groove two inches deep
and four inches wide, with a mortise at each end. wherein the front roller
and butt pinions are fixed on their axles, and over which the flat or recoil
chain traverses alternately in time of action; the forward motion for
running the gun out by centre handspikes applied to the axle of the
butt pinion, the backward motion for counteracting the recoil. In the
upper and lower plane of the body of the carriage are let in, flush and
even with the surface and fixed by eight stock or screw bolts with
counter sunk nuts, the chase plate and base plate of the carriage con-
sisting of thin slips of plate iron. The upper plate about half an inch
thick and divided into three parallel slips, the middle slip six inches in
breadth and the side slips three inches in breadth, and extending the
whole length of the body, and united at the front and butt by similar
plates corresponding with the semicircular arches. In the middle of
the upper or chase plate is made a parallel groove or opening of two
inches wide extending from within nine inches of the front roller to the
same distance of the butt pinion. The side slips of the chase plate
being united and combined with the middle slip by four stays on each
side at equal distances, the two side slips of the base plate being
three quarters of an inch thick, and three inches in breadth, are united

page_text: by four cross braces of equal strength corresponding with the four stays
in the chase plate, and through which the above mentioned stock bolts
are passed flush with the upper and lower surface of the body, forming
at once two solid and parallel planes of the greatest strength and
resistance. Upon the upper plane or chase level of the carringe is
placed the fulcrum, which is denominated either a single or double
fulcrum as it is constructed either with a single cylinder and axle or
with two parallel cylinders and axles passing through the lower frame
or sill of the fulcrum; the former being for the mounting of light
cannons such as from the twenty-four pounders downwards, and the
latter for heavy cannon such as from the thirty-two pounders upwards.
The fulcrum is also considered as constructed to a fixed or invariable
radius or to a variable or indefinite radius; the former always bearing
the centre of the trunnions to a given height above the chase level of
the carriage; the latter admitting of every degree and minute of eleva-
tion from the plane of horizon to the angle of forty-five degrees and
upwards. The parts in construction of the single fulcrum consisting of
the two side standards whereon the trunnions rest in semicular arches,
and are therein secured by the trunnion hasps or cap squares, these side
standards being united or combined by a strong round transom, and by
the wrought iron axle passing through the lower sill or frame of the
fulcrum. On this axle the chase cylinder turns and acts upon the
plane or chase level of the carriage. The sides of the lower sill or
frame of the standards being rabbetted, so as to project in upon
the chase one inch and descending one inch below its level, forms a
wide groove corresponding with the parallel sides of the chase plate,
and hereby directing the fulcrum in its alternate motion in a right line
upon the plane of the chase. To the lower frame of the fulcrum are
also attached the setting screws one on each sido of the body with a
vertical cylinder on each screw bolt for acting on the sides of the
carriage. These setting screws being tied together or united by the
base plate of the fulcrum lying below the cylinders across and under
the base of the carriage, the sill or frame of the fulcrum being at
right angles to the side standards, in the after part of which is fixed a
small axle passing through the train rings and chain staple parallel to

page_text: the axle of the chase cylinder, the staple being fixed by three or fou
rounds of the recoil chain passing through the lower part of it under
the chase plate. By this means the fulcrum and cannon are completely
secured on the carriage, but, at the same time, left perfectly free to the
direction of its motions as far as the gunner or military engineer may
consider necessary for his purpose. To the train rings placed on each
side of the chain staple on the same axle is fixed the fore end of the
train bar by a small bolt and forelock. At the after end of this bar
which lies directly under the cincture and ogee of the cascable (when
the axis of the piece lies in the plane of the horizon) are formed
the bearings or eyes through which the axle of the train cylinder is
passed, parallel to the plane of the chase in an horizontal position, and
on which the cylinder and gun screws are placed upon the gun.
Screws are brought on the bed of the cascable, in the mortices of which
at each end are the screw pinions through which the gun screws pass
in a perpendicular position on each side of the cincture. Through the
back part of the bed, under the cascable, is fixed the perpendicular
screw that drives the pinion, and by means of a winch handle gives the
uniform vertical motion required for the elevation and depression of the
gun's axis. Having above described the form and construction of the
invariable single fulerum and train, that of the invariable double fulcrum
may be now easily conceived by any engineer or mechanic, as the only
real difference consists in the former acting with a single cylinder, and
the latter with two parallel cylinders upon the chase plane of the
carriage, the cylinder on the after axle being divided into two parts
in order to give place to the train rings (if necessary) and the chain
staple upon the same axle. The side standards of the double fulcrum
may be indefinitely varied as to their form. That figure which presents
the least surface, with the greatest strength and curvature, is the best
in time of real action for rendering the shot of the enemy reflective
and ineffectual. And I here observe as one general maxim in construc-
tion, that all repellant or acute angles which may be eut by either
round or grape shot are to be carefully avoided as much as possible in
configuration of the parts of this system. The side standards of the
double fulerum, used in mounting the piece of heavy ordnance above

page_text: mentioned, are formed by describing the arch of a semicircle upon the
lower sill or frame, and an inverted arch of a small circle from the
centre of the trunnion upon the periphery of the lower' arch; the
extreme diameter of which is eighteen inches, and that of the inverted
arch where the centres of the trunnious are placed: parallel to the chase,
sixteen inches. The height of the centre of each trunnion from the
chase level is here equal to the diameter of the platband of the breech;
and this height is called the radius of the fulcrum, which constitutes
the line of the angle of elevation to the gun's axis, and may be cal-
culated to produce the angle of fifteen degrees. The side standards of
this fulcrum being rounded off in every position, and united or com-
bined by the strong segment of a large cylinder twelve inches diameter
in place of a round transon. In the lower frame or sills are four setting
screw bolts, two on each side of the body,. with their. vertical cylinders,
and with the base plate below the cylinders, as described in the single
fulcrum. Having thus. particularly explained the construction of the
fixed or invariable fulcrum; both single and double, I shall now briefly
describe the nature of that which produces the variable radius, and
consequently any degree of elevation to the gun's axis from the plane
of the horizon to the angle of forty-five degrees and upwards. This
fulcrum, whether single or double, consists of two parts; first, the lower
frame or sills which contain the chase cylinders and axles; with the
train and with the setting screws as above explained; second, the side
standard united by a round transon, and forming two parallel triangles,
the base of each resting or supported on the sides of the lower sills
which is in length equal to the base of the triangles; the perpendicular
of each triangle, or side standard, being directly under the trunnions
and sufficient to admit, in the first instance (by the train), of an eleva-
tion from ten degrees to fifteen degrees of the gun's axis, with the base
resting upon the lower sills; the inclined. plane of each triangle being
towards the breech and meeting the base or the after part of the sills,
where a strong joint is made as a centre upon which the fulcrum is
raised to produce the greatest angle of elevation; the front of each
standard or triangle-being the segment or arch of a circle, 'described. by
a radius.from, the: above joint or centre, with: the lower part of each

page_text: segment passing through a mortico on each side of the carriage in the
fore part of the sills. In this mortice, on each side behind the segments,
are fixed two strong nuts or pinions on an axle parallel to the chase
cylinders, which acting on the inside of the segments, from the axle
being turned by two men with the centre handspikes, raises the gun
and fulcrum, which at every five degrees of elevation is fixed by a strong
iron lever or stopper passing into the segments from the sill on each
sile. The fifth part in construction being the bolster or head-bearing,
combined by the tie or span iron with the legs. The bolster being a
ring or circle of cast iron placed on the plane of the fore staple with
four friction balls. The diameter of the circle being nearly equal to the
front of the carriage which it bears, and turns with it round the centre
pin. Below this is the fore staple, being an oblong plate of cast iron,
three feet in length, sixteen inches in breadth, and one inch thick,
rounded at the end, having an open groove two feet, nine inches, in
length, and three inches wide, through which the centre pin passes
from the deck or platform through the head of the carriage. In the
lower part of the forc staple are the holes through which the staple
bolt passes, and fixes the carriage by the centre pin at any given dis-
tance from the sill of the port or embrasure. Sixthly, the bar of the
fore staple being strongly secured by three iron bolts through the sill
of the port, and its step at the other end fixed by a bolt to the deck or
platform. By this means the gun and carriage are firmly preserved in
every position, and at all times correctly true to the centre of the port
or to the direct line of fire. From the bolster or head-bearing extends,
parallel to the base, the tic or span iron, one inch in diameter, which
dividing into two parts forms a triangle with the foot bar of the legs
about eighteen inches wide and the same in length, and to which it is
fixed by two screw nuts on the outside of the bar. The legs of the
carriage being two strong inverted segments of a circle made of cast
iron, standing inclined to each other, and perpendicular to the base of
the carriage, with the circular or boxfoot of each leg about four feet
apart, the upper end of each leg morticed into the butt of the carriage
with a flaunch. So as to support the whole in a correct horizontal posi-
tion under the foot of each leg, I have, at present, affixed two metal

page_text: cylinders upon a horizontal axle, which construction I recommend as
best adapted for naval service where considerable friction is frequently
necessary; but for fort service it is my intention to make use of cannon
shot which will increase the velocity of the carriage in its horizontal
range. Seventhly, and lastly, for the purpose of producing the uniform
horizontal motion or range of this system of artillery upon the deck of a
line of battle of ship or other ship of war, or on the platform of a battery.
I here apply the easiest and most powerful means possible, which is
that of a swifter, being a piece of five inch rope fastened to the centre
of the bar, and to each foot, and passing through a snatch block at a
proper distance on each side of the carriage; and with a single block at
each end of the swifter, I make use of a piece of three inch rope of
sufficient length, the end of which is fixed to the train post, and the
other immediately behind it to a staple in the deck or platform. This
train post being fixed in a vertical position in the rear of the gun directly
opposite to the centre of the port or embrasure, one man brings the
gun into position with the greatest facility. Having here explained the
construction and application of this system of artillery as employed in
marine and fort service, it is hereby my intention, under the protection
of the said Letters Patent, to construct and bring into practice such a
set of wheels as shall receive the above carriage, with its ordnance
already mounted, in manner above described, so that the same artillery
may at any time or on any occasion of necessity be taken either from
the deck of a ship of war or from the platform of a battery and brought
to action in the service of the field.
MICHAEL LOGAN. (L.B.)
80 AND BE IT REMEMBERED, that on the Twelfth day of April,
in the forty-sixth year of the reign of His Majesty King George the
Third, the said Michael Logan came before our said Lord the King, in

page_text: His Chancery, and acknowledged the Instrument aforesaid, and all and
every thing therein contained and specified, in form above written;
and also the Instrument aforesaid was stamped according to the tenor
of the Statute made in the forty-fourth year of His said Majesty's
reign.
Inrolled the Twelfth day of April, in the year of our Lord One
thousand eight hundred and six.
LONDON:
Printed by GEORGE EDWARD EYRE and WILLIAM SPOTTISWOODE;
Printers to the Queen's most Excellent Majesty. 1854.