Confine a leech in a large phial, three parts filled with rain water,
regularly changed twice a week, and placed on a window frame, fronting
the north. In fair and frosty weather it lies motionless, and rolled
up in a spiral form, at the bottom of the glass: but prior to rain or
snow, it creeps up to the top, where if the rain will be heavy and of
some continuance, it remains a considerable time; if trifling, it
quickly descends. Should the rain or snow be accompanied with wind, it
darts about its habitation with amazing celerity, and seldom ceases
until it begins to blow hard. If a storm of thunder or lightning be
approaching, it is exceedingly agitated, and expresses its feelings in
violent convulsive starts, at the top of the glass. It is remarkable
that however fine and serene the weather may be, and not the least
indication to change, either from the sky, the barometer, or any other
cause whatsoever, yet, if the animal ever shift its position, or move
in a desultory manner, so certain will the coincident results occur,
within thirty-six hours, frequently within twenty-four, and sometimes
in twelve; though its motions chiefly depend on the fall and duration
of the wet, and the strength of the wind.

_The Awn of Barley an Hydrometer._

The awn of barley is furnished with stiff points, which, like the
teeth of a saw, are all turned towards the point of it; as this long
awn lies upon the ground, it extends itself in the moist air of night,
and pushes forward the barley-corn, which it adheres to in the day; it
shortens as it dries; and, as these points prevent it from receding,
it draws up its pointed end, and thus, creeping like a worm, will
travel many feet from the parent stem. That very ingenious mechanic
philosopher, Mr. Edgworth, once made on this principle a wooden
automaton: its back consisted of soft fir-wood, about an inch square,
and four feet long, made of pieces cut the cross-way in respect to the
fibres of the wood, and glued together; it had two feet before, and
two behind, which supported the back horizontally, but were placed
with their extremities, which were armed with sharp points of iron,
bending backwards. Hence, in moist weather, the back lengthened, and
the two foremost feet were pushed forwards; in dry weather the hinder
feet were drawn after, as the obliquity of the points of the feet
prevented it from receding.

_The Power of Water when reduced to Vapour by Heat._

Whatever force wate