FERMENTATION. 
seemed to produce in him only diffidence 
and urbanity. 
The list of Mr. Ferguson’s public works 
is as follows: 1 . Astronomical Tables and 
Precepts for calculating the true times of 
new and full Moon, &c., 1763. 2. Tables 
and Tracts, relative to several Arts and 
Sciences, 1767. 3. An easy Introduction 
to Astronomy for young Ladies and Gentle- 
men, 2d edit. 1769. 4 . Astronomy explained 
upon Sir Isaac Newton’s principles, 6th edit. 
1772. 5. Lectures on select Subjects in 
Mechanics, Hydrostatics, Pneumatics, and 
Optics, 4th edit. 1772. 6. Select mecha- 
nical Exercises ; with a short Account of 
the Life of the Author by himself, 1773. 
7. The Art of Drawing in perspective made 
easy, 1775. 8. An Introduction to Elec- 
tricity, 1775. 9. Two Letters to the Rev. 
Mr. John Kennedy, 1775. 10. A third 
Letter to the Rev. Mr. John Kennedy, 
1775. 
FERMENTATION. The word fermen- 
tation, in general, is used to denote that 
change in the principles of organic bodies 
which begins to take place spontaneously 
as soon as their vital functions have ceased, 
and by them are at length reduced to 
their first principles. This has been dis- 
tinguished intp three stages, the vinous 
or spirituous, the acid or acetous, and the 
putrid fermentation. It is acertained al- 
most beyond doubt, that the vinous fermen- 
tation takes place only in such bodies 
as contain saccharine juices. In this the 
most remarkable product is a volatile, 
colourless, slight inflammable fluid, which 
mixes with water in all proportions, and js 
called alcohol, which see. The acetous 
fermentation is distinguished by the pro- 
duct known by the name of vinegar, which 
is the least destructible of the vegetable 
acids. It does not appear, however, that 
fermentation is absolutely necessary for the 
production of this acid, as there are many- 
other chemical processes by which it may 
be obtained or produced. In the putrid 
fermentation, bodies appear to be reduced 
into tiieir most simple parts. Ammonia is 
the product which has been remarked as 
the chief of this process, and is no doubt 
produced by the combination of the hydro- 
gen and nitrogen gases, which are disen- 
gaged together. See Ammonia. 
The acetous, like the vinous fermenta- 
tion, is confined to vegetable substances; 
but the putrefactive profcess is most emi- ' 
nently perceived in animal bodies. These 
either putrefy immediately ; or if the 
putrefaction be preceded by either of the 
other stages, their duration is too short to 
be perceived. It is considered as an esta- 
blished fact, that the three stages of fer- 
mentation always follow in the same order 
in such bodies, as are susceptible of them 
ail ; the vinous coming first, which is fol- 
lowed by the acetous and the putrefactive 
processes. 
The spontaneous decomposition of bodies 
is retarded by extreme cold, by sudden 
drying of the parts, or by preservation in 
closed vessels. The two first circum- 
stances necessarily retard the chemical 
effects by depriving the parts of that 
fluidity which is almost indispensably neces- 
sary in chemical processes. It will easily 
be understood that the third condition 
will retard the spontaneous decomposition 
of bodies ; when it is considered that the at- 
mosphere itself is the solvent, or at least the 
receptacle of many of the component parts 
of bodies, with which it is disposed to 
unite. In well closed vessels the parts 
of organized bodies, which are disposed to 
fly off in the elastic state, are prevented 
from escaping; and such parts as might 
form new combinations, by absorbing 
either the contents or the component parts 
of the atmosphere, are prevented for want 
of a free communication. The three con- 
ditions for the accomplishment of fermen- 
tation are, therefore, fluidity or moisture, 
moderate heat, or a due temperature, and 
the access of air"; the fermentation will 
likewise be modified according to the 
various component parts of bodies. 
In describing the vinous decomposition 
of vegetables, it will be of advantage to 
attend to that of mere sugar and water; 
the phenomena in these being more dis- 
tinct, because less modified by foreign ad- 
mixture. If a considerable quantity of 
water, holding in solution about one third 
of its weight of sugar be exposed to the 
air, at the temperature of about seventy 
degrees, after the addition of a small 
quantity of yeast, it soon undergoes a re- 
markable change. In the course of a few 
hours the fluid becomes turbid and frothy ; 
oxygen is absorbed, bubbles of carbonic acid 
gas are disengaged, which rise to tiie surface 
and break. The disengagement becomes 
more and more abundant; mucilage is 
separated, part of which subsides to the 
bottom ; and part being expanded into 
froth by the elastic fluid forms yeast. 
Daring the course of several days, these 
effects gradually come to their height and 
