Encyclopaedia Britannica, or, a Dictionary of arts, sciences, and miscellaneous literature : enlarged and improved. Illustrated with nearly six hundred engravings > Volume 1, A-AME

Theory.
A G U I C U
Vegetables operation is, that they are forced through the little
Food for holes in the fides of the tube, and come out in the (hape
. 1 ^n' ■ of worms. They are received upon linen cloths, co¬
vered with utilized paper, and dried in the heat of the
fun, or in a warm room. The fmall pieces mult be
ftirred from time to time ; and it is faid, that in lefs
than 12 hours, the preparation dries fo as to be capable
of being preferved.
The defeat of this procefs evidently is, that it is a
petty operation, which can only proceed llowly, and
upon a diminutive fcale. It is therefore unlikely to
be adopted in the great operations of an extenlive
agriculture, as a mode of preparing or preferving hu¬
man food.
At the beginning of the prefent year 1802, another
procefs for accomplilhing this important object was
cefs for con- contrived by Robert Forfyth, Ef}, advocate. Of this
verting proeefs, which has been communicated to the Board of
33
Mr For-
fyth’s pro
roots into
flour.
Agriculture, we are authorized to give the following
account :
The whole difficulty of difeovering a procefs, with
the view to render fucculent roots as ealily preferved
and tranfported, and therefore in every refped as va¬
luable as grain, feems to arife from our not having the
command of fuch a degree of Heady and vigorous, but
moderate heat, as will deprive them of their modture,
while at the lame time they are prevented from b :ng
burnt or fcorched in the way that coffee-beans are
treated before being grinded. This requifite degree
of heat may be obtained in a very cheap and eafy man¬
ner, by making ufe of the fteam of boiling water,
which never can burn any vegetable fubftance. Upon
this principle, Mr Forfyth’s procefs is founded, and is
conduced in the following manner :
1 ft, Let a quantity of potatoes, or carrots, or parf-
nips, &c. be waftied, and then cut or chopped into
very fmall pieces.
2dly, Lay them upon a metallic plate, and dry them
with the heat of fteam tranfmitted through the metal.
They are then in a ftate analogous to grain, and feem
capable of being preferved for any length of time.
3dly, Reduce them into flour or meal, by grinding
in any mill, or with any inftrument capable of grinding
grain.
The meal or flour thus prepared has no tendency to
attract moifture from the atmofphere, and may be pre¬
ferved during any length of time, if clofely preffed or
packed. Without this precaution, Mr Forfyth has
preferved it for fix months, when it had been coarfely
grinded in a coffee mill.
The drying procefs is not tedious. As potatoes
contain a great quantity of ftarch or gummy matter,
the pieces of them, while drying, are apt to adhere to
each other ; they muft therefore be frequently turned
or ftirred during that part of the operation. When
dry, they are almoft as hard as barley, and tafte fome-
what like the fkin of a roafted potato.
Carrots and parfnips contain lefs gummy matter.
They require lefs attention while drying, and do not
become fo hard. They may be grinded with eafe.
Their flour is very fweet to the tafte. Its fmell is
fragrant, and though the tafte of the roots cannot be
faid to be altered, it is rendered rich and agreeable
by the concentration produced by the procefs. This
is more particularly the cafe with regard to the parf-
L T U R E. 299
nips. Their meal, when coarfely grinded, and expofed v®g^a^es
to the air for a month or two, lofes its grateful fmell, <^lan“l
but the tafte continues unchanged. The tafte is com-
nmnicated very rapidly to lukewarm water, by pouring
it upon the meal, fo that it may probably prove of
fome value when fubjedled to the vinous fermentation ;
and it feems not improbable, that if fugar is ever to
be produced in abundance from plants of European
growth, it muft be by preparing them according to
this procefs.
Mr Forfyth performed his experiments with a fteam
apparatus, which, with fome alterations, may prove not
unfuitable, when eredled upon a great fcale. 34
A, Plate XII, A Aral low veffel of white iron, one Mr For-
foot fquare, and two inches in depth, for containing fub-^yt * ®am
fiances to be dried. _ apparatus.
B, a fmall round veffel, in which water is kept boil¬
ing by a lamp, C, with three wicks.
D, a tube, by which the fteam paffes into E, which
contains the drying veffel A, and is clofely foldered all
round to the bottom of it.
F, a tube, by which the water formed by the
condenfed fteam flows from the fteam veffel, E,
back into the boiler B, entering at the bottom of
the boiler.
G, a crooked tube, by which the fuperfluous fteam
efcapes into the open air. It is crooked, that it may
retard the paffage of the fteam when the veffel is at
work, which forces it to depofit more of its heat on
the, bottom of the drying veffel A.
H, a tube by which the boiler B is filled with hot
water,
I, a tube paffing up through the centre of the boiler,
and ferving as a chimney to the lamp C. It does not
communicate with the water in the boiler.
K ftiows the figure of the cover of the drying vef¬
fel A. The cover has a groove or gutter LL, paf¬
fing round its lower edge. The vapour which rifes
from the roots when drying, condenfes on touching the
cover, and flows down to the gutter, from which it
efcapes in the ftate of water, by a hole left for that pur-
pofe at each corner. The cover is only ufed for the
neatnefs requifite in making experiments.
The whole is fupported by four moveable feet, attach¬
ed to the corners of the drying veffel A, but not appear¬
ing in the figure. Every part of it is made of white
iron or tinned plate.
Inftead of the lamp C, a fmall iron pan filled with
pieces of burning charcoal, was fometimes ufed to keep
the water boiling, and a ftill more convenient plan 1
was at times adopted during the winter feafon. It
confifted of refting the bottom of the boiler B, upon
the front of the grate of the chamber, while a fire was
burning, the reft of the inftrument being at the fame
time fupported by a rope attached to the back of a
chair, to a nail or peg in the wall for hanging a pic¬
ture, or to any other convenient fupport. When ufed
in this laft manner, however, the inftrument has this
defeft, that the water in the tube H boils over at times
into the fire, which might be avoided, by placing the
tube on the oppofite fide of the boiler.
Upon the above contrivance, it may be remarked
that a kiln formed of a large metallic plate, heated by
the fteam of boiling water, may prove valuable in
many proceffes. In particular, it will probably be
’ P p a found