earth’s surface, produces the effect of making the alternations of heat
and cold much less violent than they would be if it were absent. The
different temperatures of its upper and lower parts produce a current
which draws the seas, and by means of the seas, the air, towards the
mean temperature. This circulation is also carried on between distant
tracts of the ocean; as we see in the case of the Gulf Stream, which
rushing from the Gulf of Mexico across the Atlantic to the western
shores of Europe, carries with it a portion of the heat of equatorial
climes to the colder northern regions, and bringing back in return
a portion of the cold from the same higher latitudes. Thus, large
portions of the earth are rendered habitable to man, which, without
the existence of such a law, would be doomed to perpetual frost
and solitude. This influence of the ocean on temperature, explains
satisfactorily some peculiarities in the climates of certain tracts
and islands, for example, why London is cooler in summer, and hotter
in winter than Paris. But though water expands by heat and contracts
by cold, there is even a limit to this law, for had there not been,
the lower parts of water would have frozen first, and thus entire
lakes, rivers and oceans, perhaps, become solid, and had they become
thus frozen, they would have remained so; for, as the heat at the
surface would not have descended far through the colder parts, the main
body of the ice must forever have remained solid, as in the arctic
circle. To obviate this great disadvantage, water contracts by the
increase of cold till we come _near_ the freezing temperature, (40°
F.) when it begins to expand and continues so to do till it freezes;
at 32° F. Hence, water at 40° is at its greatest density and will lie
at the bottom, with cooler water or ice floating above it. However
much the surface be cooled, water colder than 40° cannot descend to
displace water warmer than itself. Hence we never can have ice formed
at the bottom of deep water, though it is not uncommon to find it
thus situated, in shallow streams or rivers of rapid flow. Here the
temperature of the whole body of water is brought down to the freezing
point, and in freezing the ice adheres to the sides and bottom of the
stream. What a beautiful provision is this, that the coldest water
should rise to the surface, and there freeze and remain, exposed to
the warmth of the sun-beams and the air, to be speedily dissolved upon
the return of spring! This is owing to the well known fact, that in
the act of freezing a still further expansion takes place, so that
the specific gravity of ice is less than water of any temperature,
and consequently floats upon the surface. We thus see that by the
contraction of water by cold, the temperature of various times and
places is equalized, though were that contraction without limit, a
great portion of the earth would be bound in fetters of ice. Such a
disastrous result, is prevented by the substitution of expansion for
contraction, when the temperature is reduced to 40°, and the benevolent
purposes of an all-wise Designer, are made still more manifest by the
further expansion of water in the act of freezing. As water becomes
ice by cold, it becomes _steam_ by heat. We generally understand by
steam the vapor of hot water, but steam or vapor rises from water
at all temperatures, however low, and even from ice. The expansive
force of this vapor increases rapidly as the heat increases, but yet
in all cases the surface of water is covered with an atmosphere of
aqueous vapor, the pressure, or _tension_ of which is limited by the
temperature of the water. If, therefore, the vapor is not confined,
causing the surface of water to be pressed upon, evaporation will
take place, and thus there must, according to this law, always exist
an atmosphere of aqueous vapor, the tension of which may be compared
with that of our common atmosphere. Now the pressure of the latter
is measured by the barometrical column, about 30 inches of mercury,
while that of watery vapor is equal to one inch of mercury at the
constituent temperature of 80 degrees, and to one fifth of an inch at
the temperature of 32 degrees.
If the atmosphere of air by which we are supported were annihilated,
there would still remain, an atmosphere of aqueous vapor, arising from
the waters and moist parts of the earth, but in the existing state of
things this vapor rises _in_ the atmosphere of dry air, and thus its
distribution and effects are materially influenced by the vehicle in
which it is thus carried.
The moisture thus floating at all times in the air, serves for the
support of vegetable life, even in countries where rain seldom if
ever falls. It is absorbed by the leaves of living plants, which
thus increase in weight even when suspended in the atmosphere and
disconnected with the soil. During intense heats, and when the soil is
parched and dry, we see the life of plants thus preserved until the
earth is again refreshed with showers, and the roots supplied with
their wonted moisture.
_Clouds_, are produced when aqueous vapor returns to the state of
water; and this process is called _condensation_. Whenever the
temperature becomes lower than the constituent temperature, requisite
for the maintenance of the vapory state, some of the vapor, or
invisible steam, will be condensed, and become water. This may be
seen illustrated in the condensation of the steam, as it issues from
the spout of a tea-kettle. Clouds not only moderate the fervor of the
sun, but they also check radiation from the earth, for we find that
the coldest nights are those which occur under a cloudless winter sky.
The use of clouds in the formation of rain, is too obvious to need
pointing out more particularly. _Snow_ is frozen vapour aggregated by
a confused action of crystalline laws, and _ice_ is water, solidified
while in its fluid state, by the same crystalline forces. These are bad
conductors of cold, and when the ground is covered with snow, or the
surface of the soil, or if the water is frozen, the roots or bulbs of
plants beneath are protected by the congealed water from the influence
of the atmosphere, the temperature of which in northern winters, is
usually very much below the freezing point; and this water becomes the
first nourishment of the plant, in early spring. The expansion of water
during its congelation, at which time its volume increases one twelfth,
and its contraction in bulk during a thaw, tend to pulverize the soil,
to separate its parts from each other, and to make it more permeable to
the influence of the air.
When ice changes to water, or water to steam, although at an invariable
degree of temperature, yet the change is not sudden, but gradual.
When the heat reaches the point, at which thawing or boiling takes
place, the temperature makes a stand; a portion of it disappears, or
becomes _latent_, as it is called; thus the temperature of ice cannot
be raised, till the whole is thawed, nor that of boiling water, till
it has all been converted into steam; all the heat that is applied
being absorbed in producing these changes. Were it not for this law of
latent heat, thaw and evaporation would be instantaneous, we should be
overwhelmed with floods, at the first glow of warmth in the spring, and
in heating water the whole would flash instantaneously into steam upon
reaching the boiling point.
It is through the same relations of water to heat, that springs are
supplied--for these undoubtedly draw their principal supplies from
rain. Mr. Dalton has calculated that the quantity of rain which falls
in England is 36 inches a year. Of this he reckoned that 13 inches flow
off to the sea by the rivers, and that the remaining 23 inches are
raised again from the ground by evaporation. The 13 inches of water
are of course supplied by evaporation from the sea, and are carried
back to the land through the atmosphere. Vapor is perpetually rising
from the ocean, and is condensed by cold in the hills and high lands,
as is easily recognized by the mists and rains, which are frequent in
such regions; whence it descends through their pores and crevices,
till it is deflected, collected and conducted out to the sea, by some
stratum or channel which is water-tight, thus keeping up a perpetual
and compound circulation. In every country these two portions of the
aqueous circulation have their regular and nearly constant proportion;
and their due distribution appears to be necessary to its organic
health, to the habits of vegetables and of man. This circulation goes
on from year to year as regularly as that of the blood, in the veins
and arteries of the human system, and though maintained by a very
different machinery, is no less clearly adapted to its purposes. In
short the properties of water which regard heat make one vast watering
engine of the atmosphere, (_Whewell_.)
COMMON WATER. Under this head are included the waters commonly known as
_rain_, _spring_, _river_, _well_ or _pump_, _lake_ and _marsh waters_.
Thomson includes _ice_, and _snow water_, _spring_ and _river water_,
and _lake water_ under _rain water_, as it is from this source that
they are chiefly supplied.
RAIN WATER is the purest kind of all natural waters, though subject to
some variations. Thus, when collected in large towns or cities, it is
less pure than when obtained in the country; moreover it is usually
loaded with impurities at the commencement of a shower, but after some
hours of continuous rain it becomes nearly pure; for the first water
which falls brings down the various foreign matters suspended in the
atmosphere. In specific gravity, it scarcely differs from distilled
water. It nevertheless generally holds in solution common air, carbonic
acid, carbonate of lime, chloride of lime, and a trace of nitric acid.
If it be collected from the roofs of houses, after it has rained for
some time, it contains sulphate of lime and occasionally carbonate
of lead. The quantity of common air in rain water does not exceed 3½
cubic inches in 100 cubic inches of water; it contains more oxygen than
atmospherical air; the same quantity of rain water contains one inch of
carbonic acid gas.
These combinations, in the small quantities in which they exist, in no
degree injure the diluent properties of rain water. It is indeed to
the presence of the two elastic gases, that rain water owes the taste
which renders it palatable to animals and useful to vegetables. Ice
water, being destitute of these gases is extremely vapid; fish cannot
live in it; and it does not seem either to quench thirst or to be so
complete a solvent in the stomach as rain water. Carbonate of ammonia
is also another ingredient. It is derived from the putrefaction of
nitrogenous substances. When several hundred pounds of rain water were
distilled by Liebig, in a copper still, and the first two or three
pounds evaporated with the addition of a little muriatic acid, he
found a very distinct crystallization of sal-ammoniac, the crystals
having a brown or yellow color. “It is worthy of observation,” says
Liebig, “that the ammonia contained in rain and snow water possesses
an offensive smell of perspiration and animal excrements, a fact which
leaves no doubt respecting its origin.” It is owing to the presence of
carbonate of ammonia that rain water owes its _softer_ feel than pure
distilled water. According to Liebig, it is the atmospheric ammonia
which furnishes the nitrogen of plants. The traces of nitric acid which
have been detected in the air, are referable to the oxidation of the
constituents of ammonia; and not to the direct union of the oxygen and
free nitrogen of the atmosphere. Dr. Pereira states that a carbonaceous
(sooty) substance, and traces of sulphates, chlorides, and calcareous
matter, are the usual impurities of the first rain water of a shower.
Zimmerman found oxide of iron and chloride potassium in rain water;
other chemists have been able to detect no iron in it, but have found
meteoric iron and nickel in dew. Brande detected in it, chloride of
sodium, chloride of magnesium, sulphate and carbonate of magnesium,
sulphate of lime, and oxide of manganese. The putrefaction to which
rain water is subject, shows that some organic matter is present. The
term _pyrrhin_ (from πυρρος red) has been applied by Zimmerman to
an atmospheric organic substance which reddens solutions of silver.
Whenever rain water is collected near large towns, it should be boiled
and strained before use, as it contains less saline impregnation than
other kinds of natural waters, it is more apt to become contaminated
with lead from roofs, gutters, cisterns, and water pipes. To purify
rain water and render it useful, for the delicate purposes of chemical
experiment, Morveau recommends dropping into it a little barytic
water and then exposing it for some time to the atmospheric air.
This combines with the carbonic acid, which being the solvent of the
carbonate of lime, both it and the carbonate of baryta are precipitated
as insoluble salts. Instead of exposing it to the atmosphere, it may be
poured from one vessel to another; by which means not only the minute
portion of barytic water is dispersed through the rain water, and
brought into contact with the carbonic acid, but it involves a great
portion of air in its substance, which improves both the taste and the
utility of the fluid.
_Snow water_, as we have already stated, is destitute of air and
other gaseous matters found in rain. According to Liebig, it contains
ammonia. It has long been a popular, but erroneous opinion, that it
was injurious to health, and had a tendency to produce bronchocele.
But this malady occurs at Sumatra, where ice and snow are never seen;
while, on the contrary, the disease is quite unknown in Chili and
Thibet, although the rivers of these countries are chiefly supplied by
the melting of the snow, with which the mountains are covered. Ice is
said not to quench thirst, but on the contrary to augment it, and that
the natives of the Arctic regions prefer enduring the utmost extremity
of this feeling, rather than attempt to remove it by eating of snow,[8]
(_Captain Ross_.)
2. SPRING WATER. Rain water, when it falls on high grounds, enters the
soil and filtrates through it, until it is stopped by some natural
obstacle, when it pushes upwards, and welling out upon the surface,
forms springs; the water is therefore merely a modification of rain
water. During its passage, however, it almost always takes up some
soluble matters, which of course vary according to the nature of
the soil. It is purest when it passes through sand or gravel; in a
limestone region, it always contains more or less of the sulphate and
carbonate of lime, and it generally contains a trace of common salt,
and the usual proportions of air and carbonic acid gas. The presence of
these is detected by subacetate of lead, which displays the smallest
portion of carbonic acid or a carbonate, and nitrate of silver, which
detects the muriates by the formation of muriate of silver.
Water from melted _ice_ is perfectly wholesome, and is drunk during
the summer season, wherever the climate will admit of its being
collected and preserved at a moderate expense. In this form, it is a
luxury--almost a _necessary_--in the middle states of this country more
particularly, “where,” Dr. Dunglison remarks, “there is not a tavern on
the road, on the eastern side of the Blue Ridge, that does not furnish
ice to the traveller in any abundance.” When sea-water freezes, the ice
does not contain the salts. Consequently, when melted, it affords fresh
water, and according to the voyagers in high northern and southern
latitudes, the water has been found sweet, soft, and wholesome.
_River Water._ This is a mixture of rain and spring water, and when
deprived of the matters which it frequently holds in suspension, is
generally of considerable purity. Mountain streams, which generally
issue from siliceous rocks, and run over stony or pebbly beds, are,
for the most part, comparatively pure and soft. The river water of
New-England, and the other hilly portions of the United States,
is usually of this description, though in the time of floods, and
after heavy rains, they contain much sedimentary matter. River water
gradually deposits much of its earthy salts as it flows, and becomes
purer by exposure; it therefore generally contains less calcareous
matter than spring water; its specific gravity is less, and its taste
more vapid. It, however, more or less partakes of the nature of the
soil over which it flows; consequently some rivers, whose waters were
pure and excellent at their source, lose these properties before they
mingle with the sea. The water of the Thames, for example, in England,
which is originally very soft and pure, becomes so loaded with animal
and vegetable matter from the towns and villages on its banks, that
after being kept a month or two in a closed cask, on opening it, a
quantity of sulphuretted hydrogen gas, of the most offensive odor
escapes, and the water is so black and nauseous as to be unfit for
use. But on racking it off, it clears, depositing a quantity of slimy
mud, and becomes remarkably clear, sweet and palatable. As the matters
deposited in such rivers are merely mingled with the body of the
water, which is too large, and too changing, to admit of any permanent
taint from solution, filtration, or even the natural deposition of the
ingredients fits them for every domestic and medicinal purpose.
* * * * *
The following Table shows the solid contents of the Thames water[9]
London, and of the Croton water[10] in the city of New-York.
+-----------------------+-----------------------++----------------------+
| | THAMES WATER. || CROTON WATER. |
| +------------+----------++---------+------------+
| QUANTITY OF WATER. |_Brentford._|_Chelsea._|| At its | In the |
| 1 Gallon = 10 lbs. | Source of | Source || source, | City of |
| Avoirdupois, at | the Grand | of the || _Croton | _New-York_ |
| 62° Fah., or 70, grs. | Junction | Chelsea || Lake._ | as it |
| Avoirdupois. |Water Works | Water || |issues from |
| | Company. | Works || | the pipes. |
| | | Company. || | |
+-----------------------+------------+----------++---------+------------+
| | Grains. | Grains. || Grains. | Grains. |
|Carbonate of Lime, | 16·000 | 16·500 || 1·42 | 1·52 |
|Sulphate of Lime, } | | || ·00 | ·44 |
|Chloride of Sodium, } | 3·400 | 2·900 || | |
|Oxide of Iron, } | | || | |
|Silica, } | very | || | |
|Magnesia, } | minute | Ditto. || ·34 | ·46 |
|Carbonaceous Matter, } | portions. | || | |
|Chloride of Magnesium,}| | || ·86 | ·90 |
|Chloride of Calcium, }| | || | |
|Carbonate of Magnesia, | | || ·70 | ·84 |
| | | || | |
|Solid matter held in | | || | |
| solution, | 19·400 | 19·400 || 2·98 | 3·70 |
|Mechanical impurity, | 0·368 | 0·238 || ·34 | ·46 |
| +------------+----------++---------+------------+
|Total solid matter, | 19·768 | 19·638 || 3·32 | 4·16 |
+-----------------------+------------+----------++---------+------------+
Analysis of the Croton and Schuylkill waters, by J. C. Booth, Professor
of Chemistry to the Franklin Institute of Pennsylvania, and H. M. Boye,
of Philadelphia.
_Croton Water._ _Schuylkill Water._
In 100 gr. in 1 In 100 gr. in 1
parts gall. parts gall.
Carbonate of Lime, 45.86 2.293 53.67 2.190
Carbonate of Magnesia, 18.78 .939 11.87 0.484
Alkaline Carbonates, 16.57 .828 4.53 0.185
Alkaline Chlorides, 3.87 .193 3.75 0.153
Oxide of Iron, 2.21 .110
Silica, 7.18 .359 9.68 0.395
Organic Matter, 5.53 .276 0.88 0.036
------ -----
Parts, 100.00 grs. 4.998
Alumina and Oxide of Iron, 1.88 0.077
Alkaline Sulphates, 13.74 0.560
----- -----
Parts, 100 grs. 4.080
The Croton water was taken from the Croton dam, and when perfectly
clear was found, as appears by the above analysis to contain 4.998,
or about _five_ grains of solid matter to the gallon. The Schuylkill
water was taken from the middle basin on Fair Mount, and contained
4.08 grains of solid matter to the gallon. The Croton differs from
the Schuylkill water in containing a larger amount of the alkaline
carbonates, and of the carbonate of magnesia, while it contains less
carbonate of lime, and is entirely destitute of the alkaline sulphates,
of which the Schuylkill contains 13.74 parts in 100 of the total solid
matters, though amounting to only one half a grain to the gallon.
It appears from the above table, that the amount of impurities
contained in the Thames water, exceeds those of the Croton by nearly
six fold, and that the quantity of lime, held in solution in the
former, surpasses that of the latter, about fifteen times. The Thames
water differs also from the Croton, in the circumstance that it
contains an appreciable quantity of chloride of sodium, or common salt
of which the Croton is entirely free. There are but very few streams to
be found, whose waters contain less than 4.16 grains of solid matter
to the gallon. The carbonate of lime is held in solution by carbonic
acid, forming bicarbonate of lime. By boiling, this acid is expelled,
and the carbonate of lime is precipitated on the sides of the vessel,
constituting the _fur_ of the tea-kettle, and the _crust_ of boilers.
River water always contains a quarter or less quantity of organic
matter in suspension or solution. As a general rule, the quantity is
too small to produce any decidedly injurious effect, but physicians and
medical writers agree in the opinion that water impregnated with it to
any great extent must be deleterious. Where the quantity of decomposing
matter is too small to produce any immediately obvious effects, it
is difficult to procure any decisive evidence of its influence on
the system. When the amount is considerable, it causes dysentery and
fevers, often of a highly fatal character. In a trial at Nottingham,
England, in 1836, it was proved that dysentery of an aggravated form,
was caused in cattle by the use of water contaminated with putrescent
vegetable matter, produced by the refuse of a starch manufactory. The
fish, (perch, pike, roach, dace, &c.,) and frogs in the pond, through
which the brook ran, were destroyed, and all the animals which drank of
the water became seriously ill, and many of them died with the symptoms
of dysentery. It was, moreover, shown, that the animals sometimes
refused to drink the water, that the mortality was in proportion to
the quantity of starch made at different times; and that subsequently,
when the putrescent matter was not allowed to pass into the brook, but
was conveyed to a river at some distance, the fish and frogs began
to return, and the mortality ceased among the cattle. There are many
instances on record where troops have sickened and many died of putrid
fever and dysentery, from drinking the water of stagnant pools and
ditches or of rivers, as of the river Lee, near Cork, (Ireland,) which,
in passing through the city, receives the contents of the sewers from
the houses, and is otherwise unwholesome.
The organic matter contained in river water consists chiefly of the
exuviæ of animal and vegetable substances, but another class of
impurities consists of living beings, (animals and vegetables.) The
aquatic animals, which have, from time to time, been exhibited in this
city by means of the solar microscope, are collected in stagnant pools,
and are not found in river or well water. The quantity of organic
matter contained in the Croton must be extremely small, as this,
together with the silex, iron, and magnesia, amount to only 4/10ths of
one grain to the gallon.
WELL WATER,--or _pump_ water, as it is often called in cities, is
essentially the same as spring water, but liable to impregnation,
owing to the land springs filtering through the walls, and conveying
impurities into it. This is sometimes prevented by lining them with
cast-iron cylinders, or by bricks laid in water-cement. Dr. Percival
affirms, that bricks harden the softest water, and give it an aluminous
impregnation. The old wells must, therefore, furnish much purer water
than the more recent, as the soluble particles are gradually washed
away. It contains a greater proportion of earthy salts, and of air,
and has a greater specific gravity than other spring waters. Owing
to the fact, that it contains a larger quantity of bicarbonate and
sulphate of lime, than river water, it decomposes and curdles soap,
and is then denominated _hard water_, to distinguish it from those
waters which mix with soap, and are therefore called _soft waters_.
The reason that hard water does not form a pure opaline solution
with soap, is, because the lime of the calcareous salts, chiefly the
_sulphate_, forms an insoluble compound with the margaric and oleic
acids of the soap. Here a double decomposition ensues, the sulphuric
acid unites with the alkali of the soap, setting free the fatty acids,
which unite with the lime to form an insoluble earthy soap. Hard water
is a less perfect solvent of organic matter than soft water; hence in
the preparation of infusions and decoctions, and for many economical
purposes, as making tea and coffee, and brewing, it is much inferior
to soft water, and for the same reasons it is improper as a drink in
dyspeptic affections, causing irritation, and a sensation of weight
in the stomach. The abundance of this earthy salt in the water of
Paris, and London, of many parts of Switzerland and this country, cause
uncomfortable feelings in strangers who visit these places. It is also
said to produce calculous complaints in the inhabitants, a result which
might be expected, owing to the low solvent power of the water not
being sufficient to carry off the animal acid, which concretes in the
kidneys to form calculi.[11] Well water can be easily freed from these
earthy salts; boiling precipitates the carbonate of lime by driving
off the carbonic acid which holds it in solution; and the addition of
a little carbonate of soda precipitates the lime, if any exist in the
water. Many persons prefer the taste of hard water to that of soft, and
a change from one to the other, frequently causes a derangement of the
digestive organs. The briskness, and rapidity of this and other water
is owing to the air, and carbonic acid mixed with it. The air contained
in water, has a larger proportion of oxygen than atmospheric air, and
hence it is better adapted for the respiration of animals.