TION OF AN ARRANGEMENT OF IMPLEMENTS TO FORM A CERTAIN APPARATUS WHICH I DENOMINATED THE HYDRAULIC BALANCE, APPLICABLE TO MECHANICAL AND HYDRAULIC PURPOSES
Year: 1817

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GEORGE
MEDHURST, of Denmark Street, in the Parish of Saint Giles in the Fields,
and County of Middlesex, Engineer, send greeting.
WHEREAS His most Excellent Majesty King George the Third, did,
by His Letters Patent under the Great Seal of the United Kingdom of
Great Britain and Ireland, bearing date at Westminster, the Twenty-sixth
day of August, in the fifty-seventh year of His reign, give and grant
unto me, the said George Medhurst, my exors, adññiors, and assigns, His
especial, full power, sole privilege and authority, that I, the said George
Medhurst, my exors, adiñiors, and assigns, should and lawfully might,
during the term of years therein mentioned, make, use, exercise, and vend,
within England, Wales, and the Town of Berwick-upon-Tweed, my "INVEN-
TION OF AN ARRANGEMENT OF IMPLEMENTS TO FORM A CERTAIN APPARATUS WHICH
I DENOMINATED THE HYDRAULIC BALANCE, APPLICABLE TO MECHANICAL AND HYDRAULIC
PURPOSES;" in which said Letters Patent there is contained a proviso that
if I, the said George Medhurst, shall not particularly describe and ascertain
the nature of my said Invention, and in what manner the same is to be
performed, by an instrument in writing under my hand and seal, and
cause the same to be inrolled in His Majesty's High Court of Chancery
within six calendar months 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, shall utterly cease, determine, and
become void, as in and by the same, relation being thereunto had, may more
fully and at large appear.

page_text: NOW KNOW YE, that in compliance with the said proviso, I, the said
George Medhurst, do hereby declare that the nature of my said Invention,
and the manner in which the same is to be performed, are particularly described
and ascertained in and by the Drawings hereunto annexed, and the following
description thereof (that is to say):
It is designed to raise water and vessels, goods, or other floating bodies upon
the water, for the purpose of ascertaining the weight of such bodies, or for the
purpose of transferring vessels or floating bodies from one elevation to another,
and other purposes to which it is applicable.
The apparatus consists of a bason or pond of water A, A, Fig. 1, within
which is to be an air-tight vessel of wood or iron B, B, closed at the top
and open to the water at the bottom, and made to float upon the water by the
air enclosed within it, and also so loaded as just to float under the surface of
the water when it is full of air. This air vessel is to be connected to two
plungers S, S, by means of the two iron pillars P, P, and the timber T, T;
these plungers are to rise and fall in the two wells of water W, W. The
water in the wells must cominunicate only with the water in the receptacle
or lock in which it is intended to be raised, by means of the two channels
marked H, H, so that as the plungers descend in the wells the water will
rise in them, and also the receptaclo or lock, vice versa.
The use of the air vessel is to give the plungers and the apparatus
connected to them an equal and uniform degree of buoyancy in every
point of their elevation, which is performed by the condensation and expansion
of the air within it, as the air is more or less compressed by the incumbent
water of the bason, and by this means each side of the ballance in every part
of the range is made capable of supporting the other, for as the plungers
increase in buoyancy by descending deeper in the water, the air vessel
decreases in buoyancy by the condensation of the air under the depth of
water, and the weight of the air vessel and its apparatus as it sinks is
gradually transferred to the plungers, by which the rising and increasing
column of water in the lock is supported. The dimensions or solid content
of that part of the two plungers that is immersed in the water by their sinking
in the wells must be equal to the quantity of water that is necessary to pass
into the lock or receptacle to raise it to the height required, and the wells
must be large enough to admit the plungers to pass up and down within
them without touching their sides; and also, for the water to pass freely
between them and the sides, their depth must be equal to the depth that
the air vessel sinks in the bason, added to the heighth that the water is to
rise in the lock. The dimensions of the air vessel must be regulated by the

page_text: depth of the bason in which is to float; if the bason can be made deep enough
for the air vessel to sink 33 feet under water, so that the air within it may be
compressed into half its natural space by the pressure of the incumbent water,
then the air vessel must be capable of containing double the quantity of
water that is required to pass into the lock, &c. But if that depth cannot
be obtained for the bason, from the nature of the ground or other circumstance.
then the content of the air vessel must be inversely as the depth, viz.:
if the depth be only half 33 feet, the content must be double the
former quantity, or equal to four times the quantity of water required
to pass into the lock. The operation of raising the water is performed
by adding a weight to the air vessel, the timbers or any part of the
apparatus attached to them, sufficient to make it sink, together with the plungers,
in the wells, and as the plungers sink they will displace the water in the wells,
and cause it to flow through the channels H, H, into the lock or receptacle,
and raise it to the height required, together with the vessel and loading that is
floating upon it, and when the additional weight is removed from the air vessel
it will rise to the surface of the superior weight of water in the wells, lock, &c.;
or if the apparatus greater force to cause it to descend a rope may be
fixed upon the timbers, and connected to a spindle underneath, as represented
at a, by which a man may draw it down and raise the water in the lock, &c.,
and by turning the winch the contrary way the air vessel will reascend, and
the water in the lock, &c., will subside. A condensing air pump G must be
fixed upon the tinibers or in some other convenient spot, from whence there
may be a communication by a pipe to the air in the air vessel, in order to
supply the air vessel with air when necessary, and in the pipe of communication
must be a stop cock C, to let out the superfluous air when overcharged. If
the hydraulic ballance is designed only to weigh goods, carriages, cattle, &c.,
the exterior form will be represented by Fig. 2. E is a boat floating upon
the water in the receptacle or lock, and capable of sustaining the greatest
weight that is intended to be weighed, with a platform upon it to receive the
goods, &c. F is the scale to hold the weight, which is suspended from the
timbers of the air vessel T, T. The interior parts of the apparatus are to be
the same in form and disposion as in Fig. 1, but smaller in proportion to the
greatest weights that they are intended to sustain; but the depth of the bason
and wells need not be more than sufficient to allow the air vessel and plungers
to sink one foot. Reference A, A, the bason or pond of water; B, B, the air
vessel; S, S, the two plungers; P, P, the two iron pillars; T, T, the timbers
that connect the air vessel to the plungers; W, W, the wells; H, H, the two
channels that communicate from the wells to the lock; X, the spindle and

page_text: winch to wind the air vessel down; G, the condensing air pump; C, the stop-
cock in the pipe of the pump; E, the boat and platform; Fig. 2, F, the scale
to hold the weights.
In witness whereof, I, the said George Medhurst, have hereunto set my
hand and seal, this Twenty-fifth day of February, in the year of our
Lord One thousand eight hundred and eighteen.