WATER. 
liydrogen, combined with oxygen, in the 
proportion of 14.42 to 85.58. Water is 
assumed as the standard, or unity, in all 
tri'files of specific gravity. A cubic inch of 
it weighs, at thirty inches of the barometer, 
and 60“ thermometer, 252,422 grains. Wa- 
fer does not enter tlie list of materia me- 
dica of* any of the colleges, but it is so im- 
portant, both as an article of diet, and as 
an agent in the cure of diseases, that a 
bi'iet a( count of its varieties and properties 
cannot but be proper in this place. The 
purest natural water is melt^ snow, or 
rain, . collected in the open fields. That 
which falls in towns, or is collected from 
the roofs of houses, is contaminated with 
soot, animal effluvia, atid other impurities; 
although, after it has rained for some time , 
the quantity of these diminishes so much, 
that hlorvean says, it may be rendered al- 
most perfectly pure by means of a little 
barytic w'ater and exposure to the atmos- 
phere. Rain . wafer, after it falls, either 
remains on the surface of the earth, or 
penetrates through it until it meets with 
some impenetrable obstruction to its pro- 
gress, when it bursts out at some lower 
part, forming a spring or well. The water 
on the surface of the earth either descends 
along its declivities in streams, which, gra- 
dually wearing channels for themselves, 
combine to form rivers, which at last reach 
the sea ; or it remains stagnant in cavities 
of considerable depth, forming lakes or 
ponds, or on nearly level ground forming 
marshes. Although the varieties of spring 
waters are exceedingly numerous, they may 
be divided into, 1. flie soft, which are suffi- 
ciently pure to dissolve soap, and to answer 
the purposes of pure water in general. ' 2 
The hard, which contain earthy salts, de- 
compose soap, and are unfit for many pur- 
poses, both in domestic economy and in 
manulactnrcs. 3. The saline, which are 
.strongly impregnated with soluble salts. 
When spring waters possess any peculiar 
character, they are called mineral waters. 
See Waters, mineral. 
River water is in general soft, as it is 
formed of spring water, which by exposure 
becomes more pure; and running surface 
water, witich although turbid from particles 
of clay suspended in it, is otherwise very 
pure. Lake water is similar to river water. 
The water of marshes, on the contrary, is 
exceedingly impure, and often highly fetid, 
from the great proportion of animal and 
vegetable matters , constantly decaying in 
them. 
So early as the year 1776, an experiment 
was made by Macquer to ascertain what 
would be the product of the combustion of 
iifflammable air, or hydrogen gas. He 
accordingly set fire to a bottle full of it, 
and held a saucer over the flame, but no 
soot appeared upon it as he expected, for 
it remained quite clean, and was bedewed 
with drops which were found to be pure 
water. Various conjectures were now 
formed about the nature of the product of 
the combustion of oxygen and hydrogen 
gases.' By some it was supposed the car- 
bonic acid gas; by others it was conjec- 
tured it would be the sulphurous or sulphu- 
ric acid. The latter was the opinion of 
M. Lavoisier. Such were the experiments 
and opinions of the French chemists previ- 
ously to the year 1781. About the beginning 
of that year, Mr. Warltire, a lecturer in 
natural philosophy, had long entertained an 
opinion that the combustion of hydrogen 
gas with atinosj)heric air, might determine 
the question, whether heat be a heavy 
body. Apprehensive of danger in making 
the experiment, he had for some time de- 
clined it, but was at last encouraged by 
Dr. Priestley, and accordingly prepared an 
apparatus for the purpose. This was a 
copper vessel properly fitted, and filled 
with atmospherical air and hydrogen gas, 
which was exploded by making the electric 
spark pass through it. A loss of weight of 
two grains was observed after the comhus- 
tion. A similar experiment was repeated 
in close glass vessels, which, though clean 
and dry before the combustion, became 
immediately wet with moisture, and lined 
with a sooty matter. This sooty matter, 
Dr. Priestley afterwards supposed, pro- 
ceeded from the mercury which had been 
employed in filling the vessel. During tlie 
same year Mr. Cavendish repeated the ex- 
periments of Mr. Warltire and Dr. Priest- 
ley. He perfonned them several times 
with atmospheric air and hydrogen gas, in 
a vessel which held 24,000 grains of water 
and he never could perceive a loss of 
W’eight more than one-fifth of a grain, and 
often none at all. In all these experiments 
not the least sooty matter appeared in the 
inside of the glass. To e.xamine the nature 
of the dew which appeared in the inside of 
the glass, he burnt 500,000 grain measures 
of hydrogen gas, with about two and a half 
times that quantity of common air ; and in 
this combustion he obtained one lumdred 
and thirty-five grains of water, wlpch bad 
neither taste nor smell, and w'hen it was 
