sending a voltaic current through a liquid, you know that we decompose
the liquid, and if it contains a metal, we liberate this metal by
electrolysis. This small cell contains a solution of acetate of lead,
which is chosen for our present purpose, because lead lends itself
freely to this crystallizing power. Into the cell are dipped two very
thin platinum wires, and these are connected by other wires with a
small voltaic battery. On sending the voltaic current through the
solution, the lead will be slowly severed from the atoms with which it
is now combined; it will be liberated upon one of the wires, and at
the moment of its liberation it will obey the polar forces of its
atoms, and produce crystalline forms of exquisite beauty. They are now
before you, sprouting like ferns from the wire, appearing indeed like
vegetable growths rendered so rapid as to be plainly visible to the
naked eye. On reversing the current, these wonderful lead-fronds will
dissolve, while from the other wire filaments of lead dart through the
liquid. In a moment or two the growth of the lead-trees recommences,
but they now cover the other wire.

In the process of crystallization, Nature first reveals herself as a
builder. Where do her operations stop? Does she continue by the play
of the same forces to form the vegetable, and afterwards the animal?
Whatever the answer to these questions may be, trust me that the
notions of the coming generations regarding this mysterious thing,
which some have called 'brute matter,' will be very different from
those of the generations past.

There is hardly a more beautiful and instructive example of this play
of molecular force than that furnished by water. You have seen the
exquisite fern-like forms produced by the crystallization of a film of
water on a cold window-pane.[15] You have also probably noticed the