current is sent through this liquid the silver is severed from the
acid, as the hydrogen was separated from the oxygen in a former
experiment; and I would ask you to observe how the metal behaves when
its molecules are thus successively set free. The image of the cell,
and of the two wires which dip into the liquid of the cell, are now
clearly shown upon the screen. Let us close the circuit, and send the
current through the liquid. From one of the wires a beautiful silver
tree commences immediately to sprout. Branches of the metal are
thrown out, and umbrageous foliage loads the branches. You have here
a growth, apparently as wonderful as that of any vegetable, perfected
in a minute before your eyes. Substituting for the nitrate of silver
acetate of lead, which is a compound of lead and acetic acid, the
electric current severs the lead from the acid, and you see the metal
slowly branching into exquisite metallic ferns, the fronds of which,
as they become too heavy, break from their roots and fall to the
bottom of the cell.

These experiments show that the common matter of our earth--'brute
matter,' as Dr. Young, in his _Night Thoughts_, is pleased to call
it--when its atoms and molecules are permitted to bring their forces
into free play, arranges itself, under the operation of these forces,
into forms which rival in beauty those of the vegetable world. And
what is the vegetable world itself, but the result of the complex play
of these molecular forces? Here, as elsewhere throughout nature, if
matter moves it is force that moves it, and if a certain structure,
vegetable or mineral, is produced, it is through the operation of the
forces exerted between the atoms and molecules.

The solid matter of which our lead and silver trees were formed was,
in the first instance, disguised in a transparent liquid; the solid
matter of which our woods and forests are composed is also, for the
most part disguised in a transparent gas, which is mixed in small
quantities with the air of our atmosphere. This gas is formed by the
union of carbon and oxygen, and is called carbonic acid gas. The
carbonic acid of the air being subjected to an action somewhat
analogous to that of the electric current in the case of our lead and
silver solutions, has its carbon liberated and deposited as woody
fibre. The watery vapour of the air is subjected to similar action;
its hydrogen is liberated from its oxygen, and lies down side by side