to water in the form of heat.
There is a kind of heat called "latent heat," which is not heat at all,
but stored energy, waiting to be turned into heat, or light, or some
other active form. Properly speaking, heat is a movement of the atoms of
matter, the intensity of which is measurable in degrees, and called its
temperature. To use the term latent heat as meaning concealed heat,
which must reappear as heat, is a misnomer and is very misleading. If it
is proper to call a wound-up spring or weight latent heat then its
present use is a correct one. What was formerly termed latent heat is
simply a form of potential energy. When sensible heat that is
measurable, as temperature, disappears in the performance of some sort
of work, especially in connection with certain phenomena relating to
water, we call it--or rather miscall it--latent heat: but the phrase
would better be "stored energy."

The action of water under heat is very peculiar, and in order to get a
correct understanding of the phenomena exhibited in glacial action we
also need to understand the phenomena of water at the freezing point. As
is well known, fresh water freezes at 32 degrees Fahrenheit, and at the
moment of freezing there is a sudden expansion to such an extent that a
cubic foot of ice will occupy a much larger space than it will in the
form of water; and because it occupies so much larger space it is
lighter than the same bulk of water would be, and therefore it floats in
water.

At the point of freezing, the thermometer if placed on the ice will
register 32 degrees. If the ice is allowed to melt, the water at the
moment of liquefaction would be found to register the same degree of
temperature as the ice when first frozen. And yet there has been a vast
expenditure of energy between the points of liquefaction and
congelation, notwithstanding the temperature of ice may be lowered,
after it is formed, many degrees, which is measurable by the
thermometer. Suppose we take a piece of ice which is 10 degrees below
the freezing point and insert in it a thermometer. If now we apply heat
to this ice the thermometer will gradually rise until it reaches the
melting point at 32 degrees Fahrenheit, where it will stand until all
the ice is melted. The application of heat is going on steadily, but
there are no indications of movement in the mercury until the last trace
of ice with which it is in contact has been liquefied. After the ice is
all melted, if the appli