AN IMPROVEMENT IN THE METHOD OF PRESERVING SALT
Year: 1840

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
DAVIDSON, Salt Manufacturer, Leith Walk, near Edinburgh, in the County
of Edinburgh, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Letters Patent under the Great Seal of Great Britain, bearing date at West-
minster, the Twelfth day of May now last past, in the third year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
John Davidson, Her especial licence, full power, sole privilege and authority,
that I, the said John Davidson, my exors, adñiors, and assigns, or such
others as I, the said John Davidson, my exors, admors, 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, and Wales, the Town of Berwick-upon-
Tweed, and in all Her Majesty's Colonies and Plantations abroad, my Inven-
tion of "AN IMPROVEMENT IN THE METHOD OF PRESERVING SALT;" in which said
Letters Patent is contained a proviso, obliging me, the said John Davidson,
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 Her Majesty's
High Court of Chancellary within six calendar months 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, the said
John Davidson, do hereby declare that the nature of my said Invention, and

page_text: the manner in which the same is to be performed, are particularly described
and ascertained in and by the following description thereof, reference being
had to the Sheet of Drawings hereunto annexed (that is to say):
My said improvement in the method of preserving salt consists in packing
and enclosing salt in a box, case, or canister made of wood, and painted or
varnished over with waterproof varnish, and securely closed, in order to be
impervious to the humidity of the air, or other source of humidity, so that the
salt which is enclosed therein may be preserved from contracting dampness,
and from becoming soiled or otherwise injured, as it is liable to do in the
customary mode heretofore practised in packing salt in baskets or in lumps
with coverings of paper. And I prefer to make such box, case, or canister of
a cylindrical form; and in order to construct the same, I take thin board of
split wood of the kind called chip or scale board, made of any suitable wood,
which can be split into scale board, and which is free from any unpleasant
smell; and I cut such scale board to a suitable length and breadth to form
the cylindrical part of the box or case; suppose, for example, about six inches
broad and about thirteen long, and the two ends I then cut and thin away
with a slope or bevil, one end being so cut on one side or surface of the board,
and the other end being so cut on the opposite side or surface thereof in a
suitable manner for preparing those two ends for being joined together with
an overlapping scarf joint of about three-quarters of an inch, or even less when
the board is bent into a circular form, and its ends brought together with
their edges in contact, and one end overlapping the other at the parts which
have been thinned as aforesaid; but before thus bending and fastening the two
ends of the board together, and whilst the board is still in a flat surface, it
may be covered over or painted with two or more coats of waterproof paint or
varnish applied on that side or surface which will form the outside of the
cylinder; the paint or varnish I prefer being shell lac dissolved in spirit of
wine, and one coat thereof being allowed to dry before another is laid on, and
when the last coat has become dry. Then in order to cause the board to bend
with regularity into a circular form, and for bringing its two ends to join
together, the board is passed endways through a machine, such as is used by
tinsmiths for bending tinned plate, and which machine consists of three
cylindrical revolving rollers disposed with their axes horizontal and parallel to
each other, two rollers being below and one above the board, which rollers are
adjusted to such distances apart as that the board when passing by the
revolving motion of the rollers over the two lower rollers and beneath the
upper one, will be depressed or bended down thereby so much between the two
lower ones as to become bent or curled into the required cylindrical form, with

page_text: the ends overlapping each other. The board thus bent is then put upon a
cylindrical block of suitable size, and the overlapping thinned ends of the
board are brought in contact and cemented together with shell lac dissolved
in spirit of wine, and made of a suitable consistence to be used in the manner
of glue; the scarf joint so formed being held fast on the block until the
cement becomes dry and hard, by clamping a piece of wood over the joint to
press the overlapping ends of the board hard against the block. A cylindrical
hoop being thus formed for the side of the box or case, two flat ends are
prepared by cutting a slice off the end of a cylindrical piece of wood turned in
a lathe, which slice may be about a quarter of an inch thick, and afterwards
turned in a lathe with a circular rebate on the edge of it, to fit exactly into
the circular hoop aforesaid, the projecting edges of the rebated cover fitting
accurately the edge of the hoop. The circular slice aforesaid, which is to form
the bottom of the box or case, is inserted into its place and cemented with
cement of shell lac as aforesaid, and to make it more secure from coming out,
a few small pins, nails, or wooden pegs may be driven through the cylindrical
side into the thickness of the bottom, and after the box or case has been filled
with salt, the top or cover may be applied with its rebate inserted within the
top edge of the cylindrical side, and fastened with cement in like manner as
already mentioned respecting the bottom, and also with pins, pegs, or nails in
addition, if preferred. The outer surface of the bottom and lid of the box or
case are to be covered with paint or varnish in like manner as the surface of
the cylindrical side, and that paint or varnish, together with the cement by
which the several joints are united together being waterproof, the access of
humidity will be prevented, notwithstanding the strong disposition of salt to
attract and absorb moisture from the atmospheric air, or other source of
moisture; or the circular ends of the box may be made rather larger than the
sides, and each such end may have a circular groove turned out in its flat
surface near to its edge or circumference, in order to receive the cylindrical
side, which will thereby be securely retained when it is cemented into the
groove with waterproof cement, as before stated, or the flat circular ends may
be made lighter and thinner if they are put into the circular side and retained
between hoops made of strips of chip wood cemented within the cylindrical
side, one such hoop being within the ends, and another on the outside of the
end, which is thereby retained in place between the two hoops in the same
manner as the end or head of a barrel or cask is retained in its groove, and
although, owing to the thinness of the side of the box or case it does not
admit of a groove being cut therein for the reception of the end; nevertheless,
the two hoops which are cemented withinside the case as aforesaid, give it as

page_text: much extra thickness as is requisite to form a groove by the space or interval
between the two hoops.
Figures 1, 2, and 3 of the Drawing represent a cylindrical box, case, or
canister of the kind herein-before described; Figure 1 exhibiting it as it
appears when finished, excepting a printed paper label, which may be stuck
on the outside, with the name and residence of the Patentee, with other
information, and which paper being applied over the joint a of the cylindrical
side will conceal the same, and also give additional strength thereto. Figure 2
shews the same case dissected, A being the side; a, the overlapping joint
thereof; B, the rebated top; and D, the corresponding bottom; Figure 3 is a
section of the whole put together, wherein the same letters denote the same
parts as in Figures 1 and 2. Figures 4, 5, and 6 represent a cylindrical box,
case, or canister of the other kind herein-before described, having its two ends
E and F grooved each with a narrow groove to receive the upper and lower
ends of the cylindrical side, which side is the same as in Figure 2, all of which
are fully explained by the section, Figure 6, of the whole put together.
Figures 7 and 8 represent a cylindrical box, case, or canister of the third and
Jast kind herein-before described, having two hoops to retain its ends in place.
The cylindrical side A is the same as in Figures 2 and 5, but rather longer,
and hoops G, H, are cemented inside of the cylindrical side A at each end, to
sustain the thin circular ends I and K, which when inserted in place are
retained by other hoops L, M, also cemented into the ends of the cylindrical
side A after the ends I, K, have been inserted, all which is fully explained by
the section, Figure 8, exhibiting the whole put together. And note, the
painting or varnishing of the outside surface of the box may be deferred until
the parts are put together, or one coat of such paint or varnish may be applied
to the parts before they are put together, and the other or final coat or coats
after they are put together, as as represented in Figures 1, 3, 4, 6, and 8.
And further, one end of a box, case, or canister may be inserted and fastened
in place by any one of the three modes herein-before described and represented
by Figures 3, 6, or 8, and the other end of the same box by any other of the
three modes. And although I have mentioned varnish of shell lac as that
which I prefer, nevertheless any other kind of paint, varnish, or composition
which is waterproof may be used, provided that it is not such as will cause an
unpleasant sinell, or the parts may be painted over with one coat of any
suitable paint which will resist water, and then a final coat or coats of shell
lac or other suitable varnish laid over such paint; or, if preferred, paint may
be mixed up with varnish and laid on together. And note, although I have
described the said boxes, cases, or canisters as being of a cylindrical form (as that

page_text: which I prefer), they may be made of any other shape that may be preferred,
and when it it is required to open such case, box, or canister to take out the
salt, or a portion thereof, the cement of shell lac by which the cover is fastened
may be disjointed by applying a hot iron to the joint to melt the cement, and
then the cover can be removed to get at the salt, and may be replaced like
the lid of any other box or canister. And note, although I have mentioned
chip wood or scale board as the material which I prefer for the cylindrical side
(being the cheapest and most suitable), yet, nevertheless, pasteboard suitably
varnished might be substituted. These cases, boxes, or canisters I sometimes
construct by merely inserting the tops and bottoms within the cylindrical side,
and placing them even therewith, and fixing them either with cement or by
attaching a strip of paper, cloth, or other binder by means of paste to keep
them tight and close; and these operations may be done singly, or both
methods adopted in the same case, if preferred, or thought necessary.
And I hereby declare that I claim as new and of my Invention, the
improvement herein-before described in the method herein-before described in
the method of preserving salt by enclosing and packing the same in wooden
cases, boxes, or canisters of the kind herein-before described, and painted,
varnished, and cemented with waterproof paint or varnish and cement, so as
to preserve the contained salt from damp and injury for any length of time.
In witness whereof, I, the said John Davidson, have hereunto set my
hand and seal, this Ninth day of November, in the year of our Lord
One thousand eight hundred and forty.
5
AND BE IT REMEMBERED, that on the Ninth day of November, in
the year of our Lord 1840, the aforesaid John Davidson 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
o to the tenor of the Statute made for that purpose.