haunts me that I am in the presence of a
wonderful creation under most remarkable
conditions, and I say to myself, again and again,
"What a singular form of matter Water is!"

Water is paradoxical and contradictory in its
outward and apparent qualities. It is at once
hard and soft, yielding and resisting. It gives
way, when permitted to do so, with marvellous
facility. The slightest and lightest substance
dropped upon it is admitted to its embrace, in
strict accordance and proportion to its deserts
and its density. So small a substance as a grain
of sand is allowed to find its natural place at
the bottom. A hydrostatic or water-bed is the
easiest of couches, so easy, in fact, that some
invalids cannot bear its excessive pliancy and
complete adaptation to the form of the sleeper.
Hence the notion of Descartes and others, that
to explain the phenomena of water, its ultimate
particles must be oblong, smooth, and flexible,
lying one upon another like eels in a tub.

But water of a given temperature, confined,
is of astounding hardness; it is as good as
incompressible at that temperature: for what is a
reduction of from forty-four to forty-eight
millionth parts of its volume under a pressure equal
to that of the atmosphere? Many solid matters
—wood for instance—can be squeezed into a
much smaller than their original bulk; the
packer's art has attained wonderful perfection
in inclosing much in little space: but all the
queen's horses and all the queen's men cannot
put a quart of water into a pint bottle; the
cleverest packer in London (which is saying a
great deal) cannot economise the room of a
table-spoonful. You could sooner drive a nail
into a solid cube of steel, than you could drive
one into a cube of water enclosed in a perfectly
unyielding box. It is the unsqueezability of
water which gives its enormous strength to the
hydraulic press. The hardness of water may be
felt by striking its surface smartly with the open
hand; the quality is also known to unfortunate
swimmers who, intending to pitch into the water
headforemost, fall flat on their stomachs instead.

The fickleness of seas and sea-like lakes arises
from the extreme impressionability of water to
outward influences. But while so movable and
docile that the slightest inclination of its bottom
causes it to flow in that direction, and the
slightest breath on its surface raises a ripple,
which is magnified into mountain waves by the
impulsive force of stronger winds, water
expands and contracts, in varying temperatures,
only in quite a moderate degree.

To appreciate fully the value of what is, we
may sometimes imagine what might be instead.
Thus, what a blessing it is to the human race,
to the animate world, to all organised nature,
that water is not as expansible as oil! Great
heats would cause rivers to overflow, animals to
be smitten with apoplexy, sap-vessels to burst,
making every plant one wound, while seas in
summer would inundate the coasts which had
the misfortune to bound them. There is no
abstract cause, no fundamental reason, why
water should not be as expansible as oil.
Happily, it is not so. On the contrary, the
slight variation of which it is susceptible, tends
to our advantage and convenience.

Pure water is at its greatest density, or
heaviest and most contracted, at four degrees,
centigrade (to avoid fractions), or at exactly
thirty-nine degrees of Fahrenheit, that is at seven
degrees above the freezing point; but if the
temperature changes, either way, the water
expands. From the maximum density up to the
boiling point, the expansion amounts to four
hundredth parts of its volume—a mere nothing.
If it cools below its maximum density, it still
expands up to the freezing point. Consequently,
water which is near the point of freezing is
lighter than water that is only just a trifle
warmer. It therefore rises, and floats on the
surface, allowing the warmer stratum of water
to sink. Rivers and lakes, therefore, freeze
from the top downward (which would not happen
were the density of water to continue to increase
with increasing cold), and the fish and waterweeds
remain uninjured. Were the case otherwise
than it is—if our streams and pools froze
from the bottom—in long-continued frosts they
would become solid blocks of ice; aquatic plants
and animals would perish; and even in cases of
partial freezing, the thaw and the return to a
normal state of things would be much more
tardy than under existing circumstances. Water
still further expands at its conversion into ice;
but with that we have nothing to do. Ice is
not water, and with water alone we are dealing at
present.

The providential character of the above
arrangement is brought out into still higher
relief by the fact that, although easily heated,
water is a bad conductor of heat: that is, it does
not readily part with heat. In water kept
constantly boiling, it is the ebullition from the
bottom of the pot which causes our viands to
cook so speedily. A leg of mutton, simply
plunged into boiling water, and there left to take
care of itself without the aid of the stoker, would
take a long time even to get warm through.
Rumford fixed a plate of ice at the bottom of a
glass vessel, and then poured in cold water
enough to cover it to the depth of a quarter of
an inch, on the top of which he poured boiling
water in considerable quantity. The caloric was
so slowly transmitted from the boiling water to
the ice, that, at the end of two hours, only half
of it was melted. But if, instead of fixing the
ice at the bottom, it is allowed to swim on the
surface, it is rapidly melted by the successive
transport of the molecules of hot water from the
bottom of the vessel up to the top, where the
ice is. This experiment shows us what
consequences we should have to suffer were our rivers
and lakes to freeze from the bottom, as just now
supposed. In the temperate zones, the larger
masses of water would become perennial glaciers
which no summer heat could liquefy.

Air is said to be an invisible, water a visible
fluid. But very clear water is visible to us only
from the effects of its refraction and because we