A NEW APPARATUS FOR ASCERTAINING THE WAY AND LEE-WAY OF SHIPS AND OTHER VESSELS, WHICH APPARATUS IS ALSO APPLICABLE TO OTHER USEFUL PURPOSES
Year: 1825

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, MARK
COSNAHAN, of the Isle of Man, Esquire, send greeting.
WHEREAS His present most Excellent Majesty King George the Fourth,
by His Letters Patent under the Great Seal of Great Britain, bearing date
at Westminster, the Seventeenth day of March, in the sixth year of His
reign, did, for Himself, His heirs and successors, give and grant unto me, the
said Mark Cosnahan, His especial licence that I, the said Mark Cosnahan,
my exors, admors, and assigns, or such others as I, the said Mark
Cosnahan, my exors, admors, and assigns, should at any time agree with,
and no others, from time to time and at all times 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, and
also in His said Majesty's Colonies and Plantations abroad, my Invention of
"A NEW APPARATUS FOR ASCERTAINING THE WAY AND LEE-WAY OF SHIPS AND
OTHER VESSELS, WHICH APPARATUS IS ALSO APPLICABLE TO OTHER USEFUL PURPOSES ;".
in which said Letters Patent there is contained a proviso obliging me, the
said Mark Cosnahan, by an instrument in writing under my. hand and seal,
particularly to describe and ascertain the nature of my said Invention, and
in what manner the same is to be performed, and to cause the same to be
inrolled in His Majesty's High Court of Chancery within six calendar months

page_text: next and immediately after the date of the said in part recited Letters Patent,
as in and by the same, reference being thereunto had, will more fully and at
large appear.
NOW KNOW YE, that in compliance with the said proviso, I, tho said
Mark Cosnahan, do hereby declare that the nature of my Invention, and
the manner of performing it, is herein set forth and explained by the following
description, and Drawings hereto annexed.
I shall here observe that my Invention is intended to ascertain the way
and lee-way of ships and other vessels with a greater degree of accuracy
than by any means hitherto made known.
Fig. 1 represents a front view of my marine computist or new apparatus
for effecting the desirable purpose before named. Fig. 2 represents a front
elevation of the same apparatus, one side of the square case being removed,
and also the dial, in order to shew the internal construction more plainly.
a, a, represents a brass or other metal case, within which is contained the
spiral spring 6, 6, which rests on the bottom of the case at c; d is a brass or
other metal rod or gauge, with four equal sides and angles; this fits and is
placed within the spring, and being rather longer it has a pin passed through
it at e, extending at each end a very little beyond the diameter of the spring.
The upper end of the spring is attached to an endless chain or string f, f.
The lower end of the rod or gauge has a ring fixed in it, to which a string
or line can be made fast at pleasure. Upon one side of the rod a set of
divisions are engraved three eighths of an inch apart; these indicate pounds
weight. The intermediate space is subdivided into halves and quarters, as shewn
at k, in Fig. 8. It will be seen by the divisions that this rod can indicate
28 pounds on the front of the bar, seen drawn out in Fig. 1. Another set
of divisions are engraved, occupying exactly the same length on the bar or
rod, six eighths of an inch apart, consequently there will be fourteen of them.
which are also to be subdivided into halves and quarters. These divisions
are intended to indicate knots or sea miles. On the right-hand side opposite to
that which has the divisions for pounds marked upon it, a line of notches or
indentations are made, and on the same side of the tube or case a small key
or click is affixed. This is made of a suitable shape to be pressed into either
of the notches or indentations by the action of a spring placed under the
opposite end. This key is shewn detached in Fig. 4 upon a larger scale,
a small portion of the tube and rod being also shewn.
This appendage
produces such a degree of pressure as to prevent the bar from being drawn out
by slight jerks, but it never produces so much resistance as to prevent the
bar from being returned into the case by the action of the spring, when it

page_text: is left in a state of rest. Fig. 2, g is a brass pulley, fixed upon the axis h:
ff, is an endless chain or string, which goes round the large pulley 9, and
also round the four small pallies i, ii, i. It is made fast to the upper
end of the spiral spring b. and when the spiral spring is depressed by the
bar d, then the endless chain or string will turn the pulley 9 round, and
the hand upon the axis h, as seen in Fig. 1, will indicate the quantity or
number of knots or sea miles upon the dial. Fig. 5 represents 'a log-ship
constructed of the form I prefer. The line is made fast to the cork float m;
being about 18 inches long. The log line is made fast to the log-ship, in the
manner here shewn, and the line seen at n is used to haul it in with, and other
purposes.
Having shewn how the various parts of my improved marine computist
are constructed and combined, I shall now explain how they act in use.
When it is required to ascertain a ship's way, the log-ship is let go, the line
being fastened to it in the manner shown in Fig. 5. The other end of the
line is fastened to the ring at the bottom of the bar, as seen in Fig. 1, and
then the computist is fixed in its place at the stern of the vessel, over the
rudder head; or it may be hung by the side of the cabin window or elsewhere,
as the commander may choose, suspended by a line made fast to the ring o,
above the dial plate. When all the line is veered out, the bar d' will be
drawn out of the ease, and in proportion to the ship's velocity through the
water will be the pull made upon the end of the bar Fig. 1, and as a velocity.
that pulls out the bar, so as to shew the second division on the scale of pounds,
is equal to one knot per hour, the same will be indicated on the seale of sea.
miles or knots if it is examined, and so on in proportion. This effect is
produced by the pull upon the end of the bar causing the spring to yield,
and the degree of pull is accurately indicated by the divisions upon the bar d
that issue out from the case a, and consequently the ship's way 'may by this
simple means be very accurately obtained. As the endless chain or line is
attached to the upper end of the spring b, seen in Fig. 2, when that is pulled
down by the pin e, it draws down the chain or string ff; with it, and turns
round the pulley g in the same proportion, and then the number of knots
or sea miles are indicated by the hand or pointer upon the, dial plate, shewn
in Fig. 1. The circumference of the pulley 9 should be proportioned, that
it may exactly correspond with the length of the bar d when drawn.out, and
in that case the quantity of knots will be indicated by the dial as well as on
the stem. The back side of the case is made to open on a hinge, or it may be
mado to slide into its place, by which means the endless chain or string may

page_text: be tightened if it should ever grow slack, and although I prefer the use of
an endless chain or string, and by that means obtain the indications upon a
dial plate, yet the same indications may be obtained from the divided bar
with equal accuracy. It has been usual to obtain a ship's lee-way by fixing a
semi-compass plate to the centre of the tafferel rail of any vessel, and by
observing what division or point of the compass the ship's wake coincides with,
so as to determine her lee-way merely by the eye. Fig. 6 represents a lee-
way plate of the usual construction, but to this is added a band or pointer.
This has a ring formed on the extreme end, to which a line may be at any time
fastened. The hand or pointer turns freely on a centre or axis fixed in the
centre of the plate. The lee-way plate being fixed in its usual place (namely
the centre of the taffarel rail), a small line leads out from it to the log-ship,
and then according to the vessel's being close hauled to the wind, and con-
sequently falling off her direct course at sea, the line being attached to the
log-ship, and leading to the pointer on the lee-way plate, will, in proportion to
the quantity of lee-way which the vessel may make at any time, draw round
the pointer upon the plate, and very accurately shew the number of points of
lee-way which the vessel may then make.
And in order to identify and distinguish my Invention more clearly, I
hereby declare that it consists,―
Firstly, in the application of a spiral spring inclosed in a tube or case,
and containing within the said spiral spring a bar with proper divisions upon
it; and also in combining therewith an endless chain or string connected
to a pulley in the way I have described, which will, with the other parts
united therewith, form a more accurate instrument or apparatus for ascer-
taining a ship or other vessel's way than any other before known or mado
use of.
Secondly, by adding a hand or pointer to a lee-way plate so formed or
constructed that a line may be attached thereto, a ship or other vessel's
lee-way may be more accurately ascertained than by any apparatus hitherto
known or made use of; and I hereby further declare that the same instrument
or apparatus may be used for weighing any article within its powers, such
as provisions, &c., but I do not claim the same when applied to such
purposes.
In witness whereof, I, the said Mark Cosnahan, have hereunto set my
hand and seal, this Sixteenth day of September, in the year of our
Lord One thousand eight hundred and twenty-five.
MARK (L.s.) COSNAHAN.

page_text: AND BE IT REMEMBERED, that on the Sixteenth day of September,
in the year of our Lord 1825, the aforesaid Mark Cosnahan came before our
said Lord the King in His Chancery, and acknowledged the Specification
aforesaid, and all and every thing therein contained and specified, in form above
5 written. And also the Specification aforesaid was stamped according to the
tenor of the Statute made for that purpose.
AND BE IT REMEMBERED, that on the Sixteenth day of September,
in the year of our Lord 1825, the aforesaid Mark Cosnahan came before our
said Lord the King in His Chancery, and acknowledged the Specification
aforesaid, and all and every thing therein contained and specified, in form above
5 written. And also the Specification aforesaid was stamped according to the
tenor of the Statute made for that purpose.
Inrolled the Seventeenth day of September, in the year of our Lord
One thousand eight hundred and twenty-five.