WATER.
As the most prominent compound of oxygen, water may properly receive
the reader’s attention at this time.
He who stands upon a high cliff and looks out upon the ocean,
experiences as one of his strongest impressions that of the
boundlessness of the expanse. And it is true that the area of
terrestrial waters is very wide, for in the aggregate their waves
cover more than three-fourths of the earth’s surface. But while their
superficial extent is so great, their depths are relatively but small.
When compared to the diameter of the earth the deepest ocean seems
shallow indeed. If the waters of the oceans were dried up or otherwise
wiped away, the roughness of the dry globe would be less relatively
than the roughness of an orange. In fact the total amount of water
actually existing upon the earth’s surface is less—relatively to the
entire mass of the globe—than the amount that would remain on an
orange after dipping it into a basin of water and then withdrawing
it. Notwithstanding these facts, the amount of water is so vast in
proportion to the littleness of human beings, and it has taken so
prominent a part in the phenomena observable by man, and it has been
such a powerful agent in the geological eras of the past, that it
is not surprising that its properties and history have excited the
interest of students and thinkers of all times. In the light of modern
chemical knowledge too, its various offices create an admiration that
is heightened, the more they are considered.
The chemical history, the characteristics, the properties, and the uses
of water, all these are important chemical topics; when one considers
further, the varied forms and uses in which this familiar substance is
employed in nature and in the arts, a subject is suggested that might
well furnish material for a volume. Plainly then only a few of its more
striking adaptations can be discussed here.
[Illustration: FIG. 41.—Egyptian Water-carrier.]
Importance of Water to Living Beings.
To living animals and plants water appears to be absolutely
indispensable. The reason for this is found not only in the fact
that water forms a necessary constituent part of most living beings,
but also because it serves as a sort of vehicle by virtue of whose
properties the vital processes are conducted and through which the
vital currents flow. It is easy to understand that if the atmospheric
air, which lies wrapped about our globe like a thin veil, were suddenly
wafted away, animal life would be instantly extinguished. Now, water is
not less essential than air. Banish water from the earth, and the life
of all animal and vegetable beings would instantly take its flight.
For the blood, that living tide which courses through the natural
gates and alleys of the body, contains water to the extent of nearly
seven-eighths of its weight. Again pure, unadulterated milk, rich as it
is in solid food materials dissolved or suspended within it, contains
not far short of 90 per cent of water. And further, an examination
of vegetable products reveals in them a preponderance of water such
as would not at first be suspected. Thus the following brief table
represents facts so surprising that it is at first difficult to accept
them:
Apples contain about 80 per cent of water.
Turnips ” ” 90 ” ” ” ”
Cucumbers ” ” 97 ” ” ” ”
Finally as an extreme example among the kingdoms of life it may
be mentioned that some forms of jelly-fish, as taken from their
appropriate home in the ocean, have been found to contain not less than
99 ⁹/₁₀ per cent. of water.[6]
[6] COOKE, JOSIAH P.: _Religion and Chemistry_. New York, 1864. p. 148.
The extraordinary and incredible proportion of water in living
beings is associated with the numerous, varied, and even apparently
contradictory offices to be performed by it, and the fitness of water
to fulfil these requirements is referable further to the curious and
interesting properties with which it is endowed. But it is so familiar
to every one and so bland in its action in its relation to most
well-known substances, that the ordinary observer fails to recognize
these properties and their marvellous adaptations.
One of the properties most appropriate for presentation in this
connection is the power water possesses of dissolving gases. It is
capable of storing up within itself, concealed from human view, almost
every gas with which it comes in contact. It displays this power upon
the atmospheric air, not only in its better known relations to man and
the higher animals, but also as respects the humbler population of the
globe. It will be seen by-and-by that the air consists in the main
of a mixture of two gases very different in their properties. One is
oxygen, the sustainer of animal respiration; the other, nitrogen, the
inactive substance existing in the air as a mere diluent of the active
oxygen. Now water possesses a very curious relation to these gases; it
naturally dissolves a larger proportion of oxygen than of nitrogen.
By reason of this property it acts upon the atmospheric air with a
selective effect highly suggestive of intelligent plan. For the gas
it selects to dissolve in larger proportional quantity is oxygen,—the
one absolutely needed to take the principal part in supporting the
respiration of the countless millions of fishes that make their natural
homes in all great bodies of water.
[Illustration: FIG. 43.—Arctic explorers employing dynamite to open a
channel through the ice.]
Terrestrial Circulation of Water.
Water is the chief liquid of the great globe itself. And it carries
on here a continued and beneficent circulation which may be properly
likened to that of the living animal and plant, except that it proceeds
on the cosmical scale. This circulation may be described as starting
in the depths of the ocean, where permanent currents are constantly
flowing in certain directions. These contribute to make the seas the
highways of navies even more completely than they would be if the
waters were always at rest. A yet more striking circulatory movement
is that initiated by the volumes of moisture which rise by constant
evaporation from the temperate as well as the tropical seas. This
water, ascending into the higher atmosphere, is carried by currents
of the air hither and thither and over the land, where by mountain
ranges or other natural means adequate to this purpose, it becomes
precipitated into a solid or liquid form. In this condensed form it
is recognized as beneficent when it is in cloud masses which delight
mankind with the purity of their fleecy whiteness, or the beauty of
their gorgeous coloring as well as when it is in the form of showers
which refresh the thirsty earth, or as the snow which protects it.
The rain and snow supply the numberless rivulets that contribute to
make up rivers, and these flow joyfully to the ocean and, mingling in
its waters, return to the source from which they came. Thus has been
pictured in brief an outline of the circulation previously suggested.
Water in the Solid Form.
Again, certain properties of water in the solid form are worthy of
presentation. Perhaps it is not inconsistent with the truth to say
that they are even more plainly beneficial. Thus in the form of snow,
water appears at first sight to be an emblem of cold. But when it
falls upon the earth it becomes a mantle or coverlet, which protects
the soil from the chilling effects of the wintry season and from that
rapid loss of heat by radiation off into space which the fields would
suffer without this protective coating. And so ice, as it forms on the
surface of lakes and ponds, manifests several remarkable properties.
Of these only two will be discussed here. They are both due to its
power of expanding at the moment of solidification. Most persons make
acquaintance with this characteristic of water by the inconvenient
bursting of pitchers and pipes, recognized as a disagreeable attendant
upon the winter’s cold. When looked upon with more fully instructed
eyes, however, it is discovered to be one feature of a remarkable
system which results in great benefit to the inhabitants of the earth.
For it is plain that as water in freezing expands, it thereby becomes
relatively lighter. On this account ice floats in water, whereas solid
substances generally sink in liquid matters of their own kind. Now the
ice formed upon lakes in the winter, stays at the top and thus protects
the water below from the chill of the colder air; so it prevents the
lakes from becoming uninhabitable to the fish. The same property
prevents a lake from becoming a mass of solid from the bottom upwards,
as would be the case if the ice upon freezing went to the bottom. The
summer’s sun would hardly be capable of thawing the solid masses so
formed. This same curious fact of the expansion of ice at the moment of
its formation contributes to the fertility of the soil. Thus the water
that penetrates the crevices of rocks, expands upon freezing, chipping
off those rocks, in fact pulverizing them little by little, and so
conveying fresh and valuable materials to the earth’s soils.
[Illustration: FIG. 42.—Water in the form of cumulus clouds.]
Water as Affecting Climate.
Further, the relations of water to heat are very interesting. “The
general aqueous circulation of the earth is a great steam-heating
apparatus, with its boiler in the tropics and its condensers all over
the globe. The sun’s rays make the steam. And wherever dew, rain
or snow fall, there heat, which came originally from the sun, and
which has been brought from the tropics concealed in the folds of the
vapor, is set free to warm the less favored regions of the earth. This
apparatus in nature, although so much simpler and working without
pipes, iron boiler or radiators, is exactly the same in principle
as the steam heater which may be seen at work in almost every large
factory.”[7] In other words, when water is changed into vapor in the
tropics, heat is not only requisite to the operation, but a definite
quantity of heat is actually stored up within the vapor so produced.
On the other hand, whenever in some cooler parts of the globe this
same portion of vapor condenses into the form of liquid, that heat
that was stored within it at the tropics is immediately evolved and
contributes something to the warmth of the region where condensation
takes place. Nay more, if the water, instead of falling as rain, falls
as snow a still larger amount of heat is by this means given out into
the atmosphere. This last statement is insensibly substantiated by the
expression often heard in winter, “the weather is too cold for snow.”
This common expression, translated into scientific language, means “the
air does not possess that amount of warmth that it would manifest if
snow were now condensing in the upper air and were ready to fall.”
[7] COOKE, JOSIAH P.: _Religion and Chemistry_. New York, 1884. p. 135.
It is not only with respect to those changes taking place when the
vapor of water changes to the liquid or the solid form that its heat
relations are beneficial to mankind. No lake can change one degree in
temperature—that is, grow warmer or cooler—without at the same time
exercising a contrarywise influence upon the air about it, and thus
a regulating one. In explanation of this declaration the following
statements may be made: When, in the intensely hot days of summer, a
lake or any mass of water become influenced by the high temperature, of
course its waters become warmer. But it is a curious fact that it takes
more heat to raise the temperature of water one degree than it does to
raise the temperature of the adjoining land one degree—or in fact to
raise any other substance known, one degree. Thus it appears that a
given amount of heat applied in a summer day to a lake will be absorbed
within the waters of that lake without raising the _temperature_ of
those waters to the extent that might be expected. So then in hot
weather the lake becomes an equalizer of temperature with a tendency in
the opposite direction, that is to cool the air about it. Now in cold
weather it becomes equally beneficial, only, as might be expected, in
the opposite direction. Thus the store of heat retained by the liquid
water is given out as the lake cools. For just as the water in order to
rise one degree in temperature requires, and indeed absorbs, more heat
than any other substance known, so naturally the same water, in cooling
one degree in temperature, freely gives out the amount of heat it had
previously stored within itself, which, as has been said is greater
than that stored up by any other substance known.
Water as a Working Contrivance.
When the moisture of the tropical oceans is taken up into the air by
evaporation, the sun has thereby done a truly stupendous amount of
_work_. For has it not lifted up high into the atmosphere an enormous
weight of this liquid material? Now as the vapor is wafted over the
land preparatory to falling as rain, it has acquired a position in
which it may do a great amount of work for human uses; for every
rain-drop, falling from its lofty position in the air, acquires thereby
a momentum which represents a quantity of force, minute in each
individual case but truly vast in the aggregate. Of this sum total but
a small portion is employed for man’s industrial uses; only a minute
fractional part is harnessed to the wheels that grind his food or weave
his clothing or transform the trees of the forest into his habitations;
yet the amount he does so employ—compelling it to do his work for
him—represents an enormous total quantity. All this work done, as well
as all that might be done, by the vast quantities of water allowed to
escape and violently run to waste, is referable back again to the sun
of the tropics, which has been enabled, by reason of the wonderful
properties of water, to store up all this power within it.
In view of what has been said, the sun and the water of the tropics may
be compared not inappropriately to the chief artificial contrivances
used in modern times for generating and applying mechanical
power—boiler and engine. As an ordinary steam-boiler imparts to water
the expansive and working power of steam, and again the ordinary
steam-engine utilizes this steam power so that it may be directly
applied to the labor of man’s workshops, so the sun of the tropics
lifts the water of the ocean high up into the air, and thus may be
likened to the boiler; while the rapidly running brooks may fitly
represent an engine in motion, ready to actuate any machine to which by
proper appliances it may be attached.