C H E M 
Nature, in organizing animals, and forming their fluids 
and folids by complex compofitions, has placed in them 
a germ of deftrudlion, which developes itlelf after the 
death of the individual. This deftruftion is effected by 
the movement termed putrefaftion, which conflfls in a 
kind of fermentation, a flow decompofltion of the folid 
or fluid fubltances. Their order of compofition, being 
more complex than that of vegetable matters, renders 
them ftill more fufceptible of the putrid decompofltion. 
Animal fubltances compofed of hydrogen, carbon, 
oxygen, and azot, and frequently Itili more complicated 
by the union of fulphur, phofphorus, &c. when deprived 
of that movement, and more particularly of that reno¬ 
vation, which conftitutes animal life, are foon altered 
by more Ample attradtions between their principles, 
which have a tendency to unite two and two together. 
This re-adtion gives birth to binary compounds, fuch as 
the carbon acid, nitric acid, ammoniac, and carbonated 
hydrogen gas, which gradually efcape into the atmof- 
phere, proportionably diminifhing the quantity of ani¬ 
mal matter. It is th-us, in confequence of.a natural de¬ 
compofltion, that we perceive this animal matter foften, 
change colour and fmell, lofe its texture and form, and 
difl'ufe through the atmofphere vapours and gafes, which 
diffolve into the air, and transfer to other bodies, par¬ 
ticularly thofe of vegetables, the materials neceflary for 
their formation. 
All the phenomena of the putrefaction of animal fub- 
ftances depend on the mechanifm here explained. In the 
union of hydrogen and azot we perceive the formation 
of ammoniac, which has been deemed the principal off- 
fpring of putiefadfion. The combination of carbon 
with oxygen explains the generation and evolution of 
carbonic acid, in which all the myltery of putrefaClion 
was made to confift, about the time when gafes were 
firft difcovered. Nitric acid, to the production of which 
it is well known how much animal fubltances contribute 
in artificial nitre pits, avifes from the union of oxygen 
with azot. A certain quantity of hydrogen gas is ex¬ 
tricated, and carries off with it carbon, fulphur, and 
even phofporus : hence the various noifome fmells, and, 
perhaps the phofphorefcence, of all putrefying animal 
matter. When all thefe volatile principles have united 
two and two together, and diffufed themfelves in the 
atmofphere, nothing remains but a portion of carbon, 
combined or mingled with fixed faline fubftances, fuch 
as the phofphats of foda and of lime. Thefe relidua 
form a fort of mould termed animal earth, which fre¬ 
quently retains a little fulpliurated and carbonated hy¬ 
drogen gas, fat, and extraCI, and in this vegetables find 
in abundance the principles requifite for the formation 
of their materials. It is on this account, that the refi- 
duum of animal matter is fo proper for manure, when 
fuflieienfly conceded. A certain portion of water is 
neceflary for this putrid decompofltion of animal fub¬ 
ftances : it furniflies them with the quantity of oxygen, 
neceflary to the compofition of carbonic and nitrid acids ; 
and it contributes highly to the produdion of the putre¬ 
factive movement, by the attradions of the oxygen it 
introduces to them. It is equally indubitable, that the 
hydrogen ariling from the decompofltion of this water, 
contributes greatly to the formation of ammoniac : for 
it is a well known fad, that, when animal matters are 
diluted with a large quantity of water, they furnifli 
abundance of ammoniac in their decompofltion. 
Putrefadion, coniifting in a feries of particular attrac¬ 
tions, is modified in many different ways by external cir- 
cumllances, fuch as temperature, the medium the animal 
fubftance occupies, the ftate of the atmofphere, whether 
more or lefs light or heavy, moift or dry, &c. Thus dead 
bodies buried in the earth, immerfed in water, or fuf- 
pended in the air, are differently affeded ; and moreover 
their bulk, their quantity, their propinquity to other 
bodies, and all the varying properties of the three me¬ 
diums above enumerated, diverlify the effeds produced. 
VoL.lV, No. xS 7 . 
I S T R Y. 173 
We have proofs of this affertion, in what happens to 
bodies interred fingly, and thofe which are buried in 
numbers heaped on one another. The former, furround- 
ed with a large quantity of earth, are foon deftroyed by 
putrefadion ; the aeriform or liquid produds of which 
are abforbed by this earthy mafs, or by the atmofphere. 
The latter, not having around them this kind of earthy 
or atmofpheric recipient, remain a long time without be¬ 
ing deftroyed ; and the animal matter is wholly convert¬ 
ed into ammoniac and concrete oil, which are known to 
form a foap fimilar to that which is found in the foil of 
burying-places furcharged with dead. The phenomena 
attending the defiirudion of animal fubftances immerfed 
in water are likewife different. As new produds are 
formed, the water diffolves them, and tranfmits them to 
the air. Continual moifture, with a conftant temperature 
fomewhat above 3a 0 , favours the putrefadion of thefe 
fubftances, and their diffolution into a ftate of gas. Oil 
the contrary, a hot and dry air, volatilizing the water, 
deficcates and hardens the bodies of animals, and pre- 
ferves them almoft as well as the dry and burning land 
of Egypt, fo abounding in natural mummies. Though 
all the circumftances of putrefadion, and the almoft in¬ 
numerable varieties of the phenomena they exhibit, are 
not yet deferibed, or even known, we have difcovered, 
that they are confined to the converfion of complex fub¬ 
ftances into fubftances lefs compound ; that nature re- 
ftores to new combinations the materials which fhe had 
but lent, as it were, to vegetables and animals ; and that 
file thus accomplifhes the perpetual circle of compofitions 
and decompofitions, which attefts her power, andaemoir- 
ftrates her fecundity, while it announces equal grandeur 
and fimplicity in the courfe of her operations. 
Befide the fubjeds mentioned at the end of the two 
preceding fedions, to which the articles of t his almoft 
diredly apply, we find, in the feveral fails here enume¬ 
rated, the following dedudions: The prefervation of all 
fubftances extraded from vegetables : the feveral fpon- 
taneous alterations they undergo, the acetous fermenta¬ 
tion, the vinous, &c. the produds of thefe alterations, 
frequently employed for the purpofes of the arts : the 
produdion of ammoniac and nitric acid : the influence 
of putrefadion in the different regions of living bodies : 
the contagion and maladies produced by the effluvia of 
putrefied fubftances : the theory of the fituation and ma¬ 
nagement of hofpitals, drains, finks, layftalls, cemete¬ 
ries, See. 
Of PRACTICAL CHEMISTRY-, with the MODERN 
CHEMICAL APPARATUS. 
Pradical chemiftry teaches to deted and to know the 
intimate and reciprocal adion of bodies upon each other; 
how to feparate their parts ; and to reunite or combine 
them when feparated: and this it does by two method?, 
viz. analyfs, or decompofltion ; and fynthefis, or combi¬ 
nation. Thefe two methods are incefl'antly pradifed in 
the grand operations of nature, and of which the che- 
mift is only an imitator. 
Examples of fimple and compound Analyfis. 
Analyfs is either funple, or compound : fimple, when by 
fynthefis we can reunite the body with the fubftances 
which refult from the analyfis : but, when this cannot 
be done, it is called complicated or compound. Thus, in 
analyfing a folid body, as cinnabar, we find it compofed 
of two fubftances, mercury and fulphur. If we unite 
thefe tw’o bodies, wefhall find the fubftance appear again 
juft as it was before decompofltion : this, therefore is 
fimple analyfis. But, if we analyfe a piece of wood, the 
refults will be, 1. A matter as long and as broad as the 
piece of wood, not quite fo thick, lighter, of a black 
colour, without fmell or fibres, eafily broken; this is 
called carbon, or coal. 2. A deep-red water tinged with 
black. 3. Another water of a lighter red, lefs filled with 
denie molecules than the firft. But to unite thefe parts, 
Y y and 
