more rapidly during the night than in the day. May not the following
be a reason for this?

We have already mentioned how electric currents pass from air to earth
and _vice versa_; at night the plant is generally covered with dew and
the plant itself becomes a good conductor, and, consequently, currents
of electricity pass to each through this medium, and during the
passage convert soil elements into plant food and stimulate the upward
currents to gather up the dissolved elements and carry them to their
proper places.

From the time electricity became a science, much research has been
made to determine its effect, if any, upon plant growth. The earlier
investigations gave in many cases contradictory results. Whether this
was due to a lack of knowledge of the science on the part of the one
performing the experiments, or some defect in the technical
applications, we are not prepared to say; but this we do know, that
such men as Jolabert, Nollet, Mainbray and other eminent physicists
affirmed that electricity favored the germination of seeds and
accelerated the growth of plants; while, on the other hand,
Ingenhouse, Sylvestre and other savants denied the existence of this
electric influence. The heated controversies and animated discussions
attending the opposing theories stimulated more careful and thorough
investigations, which establish beyond a doubt that electricity has a
beneficial effect on vegetation. Sir Humphry Davy, Humboldt, Wollaston
and Becquerel occupied themselves with the theoretical side of the
question; but it was not till after 1845 that practical electroculture
was undertaken. Williamson suggested the use of gigantic electrostatic
machines, but the attempts were fruitless. The methods most generally
adopted in experiments consisted of two metallic plates--one of copper