THE ART OR METHOD OF CONSTRUCTING LOCKS FOR NAVIGABLE CANALS ON PRINCIPLES ENTIRELY NEW, AND ALSO OF IMPROVING THOSE ALREADY ERECTED, WHEREBY ANY GIVEN PORTION OF THE WATER USUALLY EMPLOYED IN THE ASCENT AND DESCENT OF VESSELS IS SAVED
Year: 1791

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JAMES
PLAYFAIR, of Russell Place, in the Parish of Saint Pancras, Architect, send
greeting.
WHEREAS His most Excellent Majesty King George the Third did, by
His Letters Patent under the Great Seal of Great Britain, bearing date at
Westminster, the Fifth day of July, in the thirty-first year of His reign, give
and grant unto me, the said James Playfair, His especial licence that I, the
said James Playfair, during the term of years therein mentioned, should
and lawfully might use, exercise, and vend, within England, Wales, and the
Town of Berwick-upon-Tweed, the Invention of "THE ART OR METHOD OF
CONSTRUCTING LOCKS FOR NAVIGABLE CANALS ON PRINCIPLES ENTIRELY NEW,
AND ALSO OF IMPROVING THOSE ALREADY ERECTED, WHEREBY ANY GIVEN PORTION
OF THE WATER USUALLY EMPLOYED IN THE ASCENT AND DESCENT OF VESSELS IS
SAVED;" in which said Letters Patent there is contained a proviso, obliging
me, the said James Playfair, by writing under my hand and seal, to cause a
particular description of the nature of the said Invention, and in what manner
the same is to be performed, to be inrolled in His Majesty's High Court of
Chancery within one calendar month after the date of the said recited Letters
Patent, as in and by the same (relation being thereunto had) may more fully
and at large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
James Playfair, do hereby declare that the said Invention is described in the
plan and description thereof hereunto annexed.
In witness whereof, I, the said James Playfair, have hereunto set my hand
and seal, this Seventh day of July, in the year of our Lord One thou-
sand seven hundred and ninety-one.
JAMES PLAYFAIR. (L.S.)

page_text: AND BE IT REMEMBERED, that on the same Seventh day of July, in
the year
above written, the aforesaid James Playfair came before our Lord the
King in His Chancery, and acknowledged the Specification aforesaid, and all
and every thing therein contained, in form above written. And also the
Specification aforesaid was stamped according to the tenor of the Statute in
that case made and provided.

page_text: depths upon the same Chain of Locks without using more water than if the Locks were all of one depth..
may
020
one
May
manner
may
be opened and shut at pleasure so that the Water
The Water which fills the Lock when a Boat is to ascend or
The nature and principal of this manner of saving water consists in letting the Water which has served to raise or fall a Boat or Bauge from the Lock pass into
Reservoirs or Cisterns whose apertures of Communication with the lock are upon different Levels and which may be placed or constructed at the side or sides of the Lock with which
they communicate or in any other contiguous situation that circumstances
render eligible which apertures
may pass from the Lock to each Reservoir or from each Reservoir to the Lock in the following
descend instead of being passed immediately into the lower part of the Canal, is let pass into these Cisterns or Reservoirs, upon different levels, then there communication
with the Lock being shut they remain full until another Vessel is wanted to pass then again the Cisterns are emptied into the Lock which is thereby nearly filled, so
that only the remainder which is not filled is supplied from the higher part of the Canal - Each of those Cisterns must have a surface not less, than that of the Lock and must
contain half as much Water as is meant to be expended for the passing of each Vessel - The Cistern the most elevated is placed tivice its own depth (measuring by the
aperture or communicating opening of the Cisterns) under the level of the Water in the higher part of the Canal - The second Cistern is placed once its own depth under the first
and so on
are the others to the lowest which last is placed once its own depth above the level of the Water in the lower part of the Canal. The apertures of the intermediate
Cisterns whatever their number be, must all be qually divided into different levels The surface of the Water in the one • being always upon the level of the bottom of the
Aperture of the Cistern, which is immediately above. an example of the manner and rule for constructing these Cisterns, which it is my duty and desire to render as
clear as possible Suppose that a Lock is to be constructed Twelve feet deep, that is, that the Vessel may ascend or descend twelve feet in passing Suppose the Lock Sixty feet long
and six feet wide; the quantity of Miter required to fil the Lock and to pass a Boat is 4320 Cubic Feet, and suppose that in calculating the quantity of Water that can be
procured for supplying the Canal after allowing for caste it is found (according to the number of Boats that may be expected to pass) that there will not be above Eight ("
hundred Cubic feet for each then it will be necessary. save five sixths (5/6) of the whole quantity, that in the common Case would be necessary. To do which Ten Cisterns must
be made (The mode of placing which are expressed in the Drawing Figure 2) each of which must be one foot deep or deeper at pleasure and each must have a surface of Thes
hundred and sixty feet square equal to the surfice of the Lock, The bottom of the aperture of the twest Cistern must be placed one Foot above the Level of the Winter in the lower part
of the Canal, or eleven Feet under the level of the high Water . _ The second cistern must be two feet above the level of the low water, the third three feet, and so of the
others the bottom of the tenth or uppermost istern being ten feet above the low water, and two Feet lower than the high Water. And as each Cistern must be twelve, inches
in depth the surface of the Water in the higher Cistern will be one foot under the level of the Water in the upper part of the Canal. The Cistens being thus constructed
when the Lock is full and the Boat to be let down Then the communications between the Lock and the Cisterns which until then have all been shut are to be opened
in the following manner. First the communication with the higher Cistern is opened which being a the bottom, two feet under the Level of the Meter in the Lock, is filled to the
depth of one foot, the Water in the Lock iscending foot, also at the same time, that cummunication is then shut, and the communication between the Lock and the
Second Cistern is opened, one foot more of the Water then passes into that Cistern from "the Lock and fills it : the opening is then shut. The same is done with the 3rd
4th 5th 6th 7th 8th 9th and 10th Cisterns one by "'intil they are all filled and when the tenth or lowa most Cistern is filled there remams but two feet depth of Water in the Lock The
communication between the Lock and the lour part of the Canal is then opened and the last two feet depth of water are emptied wits the lower part of the Cancel. By this means it is evident
that instead of twelve feet deefe of water being hit descend into the lower part of the Canal there are only two feet depth that descend or one sixth of the whole therefore instead of 4320 Cubic
feet being used there are only 420 Cubic feet we. The remainder of the Water in the Cisterns being ised as follows When another Boat is to mount the Sluices which are then shut and
the Boat in the Lock the "Tenth or lowermost estern is emptied into the Lock which it fills one pot. The communication being then sheet, the next lowest Cistern or the 9th is emptied
into the Lock which is thereby filled another Foor and so in like manner all the other Cisterns ave emptied one after another until the higher Cistern being emptied which fills the Tenth
foot. of Water in the Locks there remains but two feet of Water to fill which is done from the upper part of the Canal by opening the higher Sluice to pass the Beat .
by that
the same quantity of water descends from the spper part of the Canal into the Lock that in the other case descended from the Lock into the lower part of the Carrill, so that in both
cases the same quantity of water is saved, that is 5/6th of what would be necessary were ther no Cisterns, Suppose again that upon the same Canal and mimediately after the tweler
feet lock it would be advantageous to construct oe of eighteen feet then in order not to use any geater quantity of water it will be necessary to have sixteen bistens espon different levels or
communicating with the Lock in the same manner should agam a Lock of only six feet be wand after that of lighten then it will only be necessary to have (Fig: 1) force listuns on
different levels and so of
height of Lok. The Rule is this for finding the number and so of the Cisterns, each astern being the same in Superficies with the Lock its depth must
be such as to contain one half the quantity of Water meant to be used in the passing of one Boa - The depth of the Lock divided by the depth necessary for such Cistern will give in all
cases the whole number of Cisterns and two me deduct the number two therefore from the number which you find by dividing the depth of the Lock, by the depth of one Cistern, and
you have always the number of Cisterns required which are to be placed upon different levels according to the Rule already given - The above is the principle and manner of using the Lock
for saving Water in Canals and for enabling ligineus to construct Locks of different depths upon se same Canal without using more Mater for the Deep locks than for the Shallow
ones with regard to the manner of disposing the Cisterns the circumstances of the Ground the eclivity &r will be the best Guide for the Engineer, I have however joined plans of two
different methods of disposing them Fig. 1 is 'v lock where there are only four Reservoirs wanter. Fig: 2 is one where there are ten wanted and Fig 3 is the Section of a Lock
24 feet deep where in order to prevent too reat a shain from the weight of Water upon the lover Stuice an Arch of Stone or Brick
be thrown over the lower part of the Canal
under which Arch the Boats may pass and against which the Flood Gates of the Lock will rest apported - I'n putting this method in practice to save expence as there can never be any
great pressure of Water in any of the Cisterns & propose to make the bottom of Clay and to surend them with Brick or hever Stone - as to the Lock itself it is constructed in the
usual manner except for the communication with the Cisterns and as it is necessary to avol any accidents from these communications being left open when they ought not so
to be there may be two valves upon each the one to shut when pressed upon by the wier in the Lock and the other to shut when pressed upon by the Water in the Cistern
which will be the case alternately as the Miler is higher in the one or in the other so that here will never be any communication except when the Valves are opened intentionally to let
the water pass Fig. 1. The Section shows the Levels of the different Cisterns according to the pinciple laid down and the plan shews only the manner.
of disposing than one by the
side of the other with one end towards the Lock which position is in general the most covenient. Fig: ? shews the Lock with ten Cisterns, it is to be observed that as these
may
be covered the Horse Road will not be intercepted by them though they are on both sides of the Canal In order to have as nearly equal pressure as possible
both sides of the Lock I have put the two Cisterns that are nearest upon the Livel n the opposite sides of the Lock so that Fig! 1 and 2 in place of being beside wich i
other are separated by the Canal itself though that precaution is not by any means necsary Fig: 3 is only made to shew the way of it throwing
-pact of the Canal to sustain the weight of Water which would otherwise be too great for the Sluice or Flood Gates.
Cisterns
on
any
other
-
11
may
means
an Arch over the lower
Drawn on Stone by Malby & S