and to whom few would refuse to submit. (May
2nd, 1832.)

* * * * *

To the Editor of the "Agricultural Gazette."

In a leading article of the 10th of January, 1852, after an
account of the effects produced on water by radiation and the
protection afforded to plants by the ice with which ponds are
covered in winter, you go on to say that there are some
circumstances under which water-plants suffer greatly, and from a
singular cause, but one which when looked into is sufficiently
simple and intelligible. As you do not appear to have hit upon the
true reason, allow me to quote a little further, and then give my
reason for this singular effect.

You say that on a very fine but still night, water is cooled less
rapidly than the earth: under such circumstances the bottom of the
pond cools more rapidly than the surface, the plants become
colder--in fact, some degrees below the freezing-point, &c. &c.

I submit that such reasons are inadmissible, for there would be an
immediate upward current, which, as water is such an excellent
conductor of heat, would immediately equalize the temperature of
all the water above 40 degrees Fahrenheit, and stratified (if I
may use the expression) above the water of this temperature there
would be another layer of water of equal but gradually decreasing
temperature until it fell below 32 degrees Fahrenheit.

The explanation I offer is this. It is well known that if water is
kept perfectly still it may be cooled down considerably, or at
least some degrees below 32 degrees, without freezing; but the
moment it is shaken a portion of it is converted into a spongy,
porous ice, and the temperature rises to 32 degrees.

What may be the case in the rivers of the South of England I do
not know, but in the rapid streams of the North this process may
be seen on a very extensive scale in severe frosts. The water in
the still pools (before they are frozen over) is cooled down to
below 32 degrees, and so soon as this cooled water reaches the
next stream, precipitation (if I may so call it) takes place, and
the spongy ice lays hold of every projecting pebble, which serves
as a nucleus in the same way as threads and bits of stick serve in
the crystallization of salts. After a severe frost, when followed
by bright sunshine the next morning, I have seen thousands of
these bits of spongy ice rising from the stones to which they had
been attached to the surface of the water. I have seen after long-
cont