F I 
place of the air thus carried out of the room is fupplied 
by frefli air coming in through doors and windows, or, 
if they be (hut, through every crevice with violence ; 
or, if the avenues to the room be fo clofed up, that little 
or no frefli fupply of air can be obtained, the current up 
the funnel mu ft flag; and the fmoke, no longer driven 
up, will float about in the room. 
Upon thefe principles, various contrivances of fire¬ 
grates and ftoves have been devifed, from the old very 
open and wide chimney places, down to the prcl'ent dole 
ones, which are much narrowed in the front, opening, by 
fide and back jambs, and a low breaft or mantle, beliaes 
the convenience of a flap, called a regifter, that covers 
the top of the fire-fiove, but opening to any degree with 
a fmall winch, which lifts the back part Hoping upwards, 
and fo throws the fmoke freely up the funnel, and yet 
admitting as little air to pafs as you pleafe ; by which 
fimple means the warm air is kept very much in the 
room, while the narrow and doping orifice promotes the 
briflc afcent of the fmoke, and yet prevents its return 
down again, for the fame reafon. 
The conflmdlion of fire-places and grates has of late 
been confiderably improved under the direction of the 
ingenious count Romford, vvhofe grand defign in thefe 
labours has been to employ fcience and philofophy to in- 
creafing the comforts and conveniences of domeftic life. 
His obfervations on the mode by which rooms become 
warm through the medium of artificial fires, are full of 
intereft, and merit attention from all perfons who regard 
their health.—“ In all our reafonings and fpeculations 
relative to the heating of rooms by means of open chim¬ 
ney fires, (fays the count,) we muft never forget that it 
is the room that heats the air, and not the air that heats 
the room. The rays that are fent off from the burning 
fuel generate heat, only when and where they are flopped, 
or abforbed, consequently they generate no heat in the 
air in the room, in palling through it, becaufe they pafs 
through it, and are not flopped by it ; but, (Inking againft 
the walls of the room, or againft any folid body in the 
room, thefe rays are there flopped and abforbed, and it 
is there that the heat found in the room is generated. 
The air in the room is afterwards heated by coming into 
contact with thefe folid bodies. Many capital miftakes 
have arifen from inattention to this mod important fa£t.” 
—The count then forcibly illuflrates the bad effects that 
muft refult from the prefent method in which our apart¬ 
ments are generally warmed. A large open fire-place, 
containing a great quantity of burning fuel, throws out a 
copious ftream of heat, which fcorches the part of the 
body turned towards it, while the temperature of the 
other fide is chilled by the rapid currents of cold air 
which are traverling the room in all directions, in order 
to fupply the enormous wade of air confumed in the 
chimney. Hence we muft be at once fenlible of the fu- 
perior advantage of a fire-place, in which lets heat indeed 
is generated, but by which it is enabled to diffufe itfelf 
more equably through the room, and a fmaller portion 
of it carried up the chimney : and hence we perceive the 
great utility of doled fire-places, regifter ftoves, and 
other fimilargrates, invented by this judicious philofopher. 
Another apparatus, called the Penfylvania fire-place, 
was invented by Dr. Franklin., by which a room is kept 
very warm by a conflant fupply of frelh hot air, that 
pafles into it through the (love itfelf. See the articles 
Grate, Stove, Sec. 
FIRE-POT, J'. in the military art, a fmall earthen pot, 
into which is put a grenade, filled with fine powder till 
the grenade be covered ; the pot is then covered with a 
piece of parchment, and two pieces of match laid acrofs 
and lighted. This pot being thrown where it is defigned 
to do execution, breaks and fires the powder, and this 
again fires the grenade, which ought to have no fuze, 
that its operation may be the quicker. 
FIRE-RA'SANT, in military taftics, a firing from 
the artillery and fmall arms, diredled parallel to the 
R E. 399 
horizon, or to thofe parts of the works of a place that 
are defended. 
FIRE-RESI'DUUM, f. in combuflion, the calx or 
cinder produced from a burnt body.—See the article Che¬ 
mistry, vol. iv. p. 195. — It often happens, after the ca¬ 
lamity of great fires, that the calces or cinders are capable 
of being converted to many ufeful purpofes, and by this 
means of refloring to the unfortunate fufferers fotne part 
of the Ioffes they might have fuftained. This fact lias 
been very recently proved by fome ingei ions and inte- 
refting experiments, made by Mr. Matthew Gregfon of 
Liverpool, upon the burnt materials remaining after the 
dreadful fire in that town, which happened in Septem¬ 
ber, 1S02. Thefe experiments were communicated to the 
Society for the Encouragement of Arts, Sec. in the Adel phi, 
London, on the 15th of March, 1803, and for which the 
focietv unanimously voted Mr. Gregfon their gold medal, 
value thirty guineas.—We (hall give the particulars of 
thefe experiments in the author’s own words : 
“ I was not prefent at the late dreadful fire in Liver¬ 
pool, when fo many large warehoufes were burnt to the 
ground, and the greateft part of their contents deftroyed 
to an imm nfe amount. I returned.home about ten days 
after the accident; the ruins yet fmoking, and the articles 
ft ill burning. The firfl time I went to the fpot, 1 col- 
ledled the following fpecimens, a part of which accom¬ 
pany this letter. 
N°. 1, is burnt fugar, marked S.B. or fweet black. 
2, is burnt wheat,-V. B. or vegetable black* 
3, is burnt rice, -R. B. or rice black. 
4, is burnt fine American barrel flour. 
5, is burnt cotton. 
Thefe are accompanied with an account of the amount' 
and fales of the damaged articles of every defeription, 
which produced, as nearly as can be efiimated, 13,050!. 
I have likewife attempted an eftimate of what might have 
been ftill further faved to individuals, and to the public,, 
to infurance offices, &c. if the plan I have lince formed 
had been then adopted. On the article of grain only, 
I eftimate the laving to be forty-four thoufand pounds more 
thanzoas recovered, which is far more than three times the. 
fum on this one article alone; and I conclude this having 
to be nearly as much again upon rice, fugar, molaffes, 
cotton, coffee, hemp. Sec. Fully imprelled with this 
idea, I wifli to make known, for the public benefit, my 
invention for converting thofe ruins, after a fire, to the 
meft ufeful purpofes; and I very much wonder, that hun¬ 
dreds who law the ruins, did not attempt fomething for 
the recovery in part of this valuable property, which waS- 
configned to the dunghill, or carried away by the tide. 
N°. 1. The burnt fugar was reduced to a fine powder, 
and was tried as a water-colour paint. As a varnifh- 
ground it is valuable; and as an oil-colour, it is ufeful 
upon mahogany. It was tried as a printing-ink, and 
proved very good. 
N°. 2. Burnt wheat was only reduced to a fine powder. 
This all’o produced water-colour, varnifh, and oil colour; 
and as a printing ink the colour was good.—My painter, 
not having the leaft knowledge of what he was ufing, 
gave it as his opinion, that either of them are preferable 
to ivory or lamp black ; that they have a good body in oil, 
and fpend freely in water. He likewife further ftates, 
that the vegetable black, as I call it, is of a ftronger body, 
and of the two is the bell black in oil, being a folid good 
colour, and drying very rapidly. He prefers the S.B. 
or fweet black, in varnifh ; and in water he conceives it 
to be a better, warmer, and richer, colour, than any In¬ 
dian ink he ever tiled ; and it much refenibles that article, 
working full as freely, and fpending!equally well. Among 
thefe fpecimens, N°. 3, marked R.B, or rice black, dries 
better than that marked V.B. 
M°. 4, is afpecimen of American fine flour, which when 
dug up was in the form of the calk, the fame being burnt, 
and the flour left brown. I have converted a part of it 
into brown powder for hair, which is not very falhionable 
at 
