warmer than the air, and so would give out or radiate its heat until a
thermometer, placed either in the room or in the water, would mark
thirty-two degrees above zero. At this point the water would begin to
freeze, but plants or vegetables would not. They would require slightly
severer cold to affect them. But as soon as the water begins to freeze it
also gradually gives out its latent heat, and before a particle of ice
can form it must give out one hundred and forty degrees of heat to the
air and water around it. Therefore the freezing process goes on slowly,
and both the air and water are kept comparatively warm. After a time,
however, the ice becomes so thick over the surface that the freezing goes
on more and more slowly, because the latent heat in the unfrozen water
cannot readily escape through the ice. It is therefore retained, just as
the latent heat in the water of an ice-covered pond is retained."

"It follows, then," said Leonard, "that after the water beneath the ice
in the tub began to freeze slowly, the flower-room, in that same degree,
began to grow cold."

"Certainly, for only as the water freezes can it give out its latent
heat. The thick wooden side of the tub is a poor conductor; the ice that
has formed over the surface is even a worse, and so the water within is
shielded from the cold. It therefore almost ceases to freeze, and so
becomes of no practical use. An intelligent understanding of these
principles is of great practical value. If I could have waked up and
placed another tub of water in the room at two or three o'clock, or else
taken all of the ice out of the first one, the process of freezing and
giving out heat would have gone on rapidly again, and none of the plants
would have suffered. I have heard people say that putting water in a
cellar was all a humbug--that the water froze and the vegetables also. Of
course the vegetables froze after the water congealed, or the cellar may