IMPROVEMENTS IN PROPELLING VESSELS
Year: 1848

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, MOSES
POOLE, of the Patent Office, London, Gentleman, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Royal Letters Patent, under the Great Seal of the United Kingdom of Great
Britain and Ireland, bearing date at Westminster, the Twenty-sixth day of
May, One thousand eight hundred and forty-eight, in the eleventh year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said Moses Poole, my exors, adñiors, and assigns, Her especial
licence, full power, sole privilege and authority, that I, the said Moses Poole,
my exors, adñiors, and assigns, and such others as I, the said Moses Poole, my
exors, adñiors, or 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 in the Islands of Guernsey,
Jersey, Alderney, Sark, and Man, and in all Her said Majesty's Colonies and
Plantations abroad, the Invention of "IMPROVEMENTS IN PROPELLING VESSELS,"
communicated to me by Lieutenant-Colonel Sir T. Livingston Mitchell, from
abroad; in which said Letters Patent is contained a proviso, that I, the
said Moses Poole, should cause a particular description of the nature of the
said' Invention, and the manner in which the same is to be performed,
by an instrument in writing under my hand and seal, to be inrolled in Her
said Majesty's High Court of Chancery within six calendar months next and

page_text: immediately after the date of the said in part recited Letters Patent, as in
and by the same, reference being thereunto bad, will more fully and at large
appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
Moses Poole, do hereby declare that the nature of the said Invention, and the
manner in which the same is to be performed, are fully described and ascer-
tained in and by the following statement thereof, reference being had to the
Drawing hereunto annexed, and to the figures and letters marked thereon,
that is to say:-
The Invention consists of applying an instrument in the nature of a
"Bommareng," placed on a suitable axis as a propeller for propelling vessels.
And in order that the Invention may be most fully understood and readily
carried into effect, I will proceed to describe the Invention as communicated
to me by Lieutenant-Colonel Sir T. Livingston Mitchell.
DESCRIPTION OF THE DRAWING.
On observing the motion of a "Bommareng," it is found to describe in its
rotatory movement in the air a whirl round a hollow centre, leaving a vacant
centre of gravity, and it suggested itself to the mind of the said Lieutenant-
Colonel Sir T. Livingston Mitchell, that this centre might be in a line such
as a, b, Figure 1, dividing the two excentric parts, so that they should be
together equal in surface to the remaining central portion; and on experiment
this view was confirmed, and he considers that this will prove to be the best
form for the application of the screw principle in propelling vessels.
Figure 2 shews the propeller in different positions, and it will be perceived
that the edges opposed to the water at d and e work in it obliquely to the
radius of rotary motion f. g, much in the manner in which a shell-auger
penetrates wood; and it will be obvious, that in this construction there will be
no tendency to throw the water into a cone.
Figure 3 shews an edge view of the propeller and axis. Great velocity of
rotatory movement appears to be desirable for the purposes of propulsion;
when the screw principle is applied, this is to be attained by the present
arrangement; where there is least lateral resistance a thin edge working in
the water obliquely can offer little obstruction, and at the centre, where
motion is slowest, the given power is kept clear of the plane of the screw.
This propeller works in the centre plane of a screw, except at the centre, and
with edges meeting the lateral resistance obliquely. The pitch of the spiral
blade or screw may be varied; the propeller may be made with a concave
and a flat surface, or with two flat or two convex surfaces; when two flat

page_text: surfaces, however, are used, it will be desirable to chamfer off the edges. The
propellers thus formed are suitable to be applied in like manner to the screw,
and such like propellers heretofore used, and more than one such blade may
be applied, but it is considered that one blade is the best.
Figures 4 and 5 shew two diagrams of such a propeller, supposing it to be
in action, from which figures it will be evident, that the two ends of the
propeller work in the thread of the same screw; the leading end a, cutting into
the water with a thin edge, may be termed the fang; the following end b,
taking the water obliquely and operating against the water so as to make its
resistance afford a purchase to drive forward this end, may be called the tail
or fin.
It will be evident that, in turning the palm in the opposite direction,
the action of a and b will be reversed, the fang becoming the fin, and vice
versâ. There is much in this peculiar difference between the real screw and
the rotatory paddles now in use, that will prove by experience how important
it will be for the attainment of high speed to adopt the true principle of the
screw. The rotatory paddles or palms, if considered as screws, may be said
to describe the threads of a double screw, each presenting a plane which,
when in motion, is opposed obliquely to a fluid which must be thrown thereby
into circular or excentric motion, whereas the thin edge of a, b, passes easily
without opposing any surface to lateral resistance through the water, and
obtains from the resistance of the fluid a propelling power, which may be
increased in proportion to the velocity.
In the instruments hitherto used called screw propellers, the lateral resist-
ance encountered in all attempts at high speed must be insurmountable, if,
according to Hutton, "the real resistance to a plane by a fluid acting in a
direction perpendicular to its face is equal to the weight of a column of the
fluid whose base is the plane;" or, "if the resistance increases as the cube of
the velocity," it must be obvious, unless the true principle of the screw is
applied, great velocity through water, by means of rotatory motion, need not
be attempted. It should be remarked, that, although I believe that the
arrangement above given is the best for combining the axis of motion to the
Bommareng propeller, I do not confine the Invention thereto, as variations
may be made without departing from the principle of the Invention.
In witness whereof, I, the said Moses Poole, have hereunto set my hand
and seal, this Twenty-fifth day of November, in the year of our Lord
One thousand eight hundred and forty-eight.
MOSES (L.s.) POOLE.

page_text: AND BE IT REMEMBERED, that on the Twenty-fifth day of November,
in the year of our Lord 1848, the aforesaid Moses Poole came before our
said Lady the Queen in Her Chancery, and acknowledged the Specification
aforesaid, and all and every thing therein contained and specified, in form above
written. And also the Specification aforesaid was stamped according to the
tenor of the Statute made for that purpose.
Envelled the Twenty fifth day of November in the roar of our Lord One
Enrolled the Twenty fifth day of November, in the year of our Lord One
thousand eight hundred and forty-eight.