its oxygen should not be exhausted, the carbonic acid given out by
breathing would very soon so contaminate the whole that life would be
impossible. To eliminate this element it would only be necessary to
carry a certain quantity of lime-water, easily calculated, and by
means of a fan or similar instrument to drive the whole of the air
periodically through the vessel containing it. The lime in solution
combining with the noxious gas would show by the turbid whiteness of
the water the absorption of the carbonic acid and formation of
carbonate of lime. But if the carbonic acid gas were merely to be
removed, it is obvious that the oxygen of the air, which forms a part
of that gas, would be constantly diminished and ultimately exhausted;
and the effect of highly oxygenated air upon the circulation is
notoriously too great to allow of any considerable increase at the
outset in the proportion of this element. I might carry a fresh supply
of oxygen, available at need, in some solid combination like chlorate
of potash; but the electricity employed for the generation of the
apergy might be also applied to the decomposition of carbonic acid and
the restoration of its oxygen to the atmosphere.

But the vessel had to be steered as well as propelled; and in order to
accomplish this it would be necessary to command the direction of the
apergy at pleasure. My means of doing this depended on two of the
best-established peculiarities of this strange force: its rectilinear
direction and its conductibility. We found that it acts through air or
in a vacuum in a single straight line, without deflection, and
seemingly without diminution. Most solids, and especially metals,
according to their electric condition, are more or less impervious to
it--antapergic. Its power of penetration diminishes under a very
obscure law, but so rapidly that no conceivable strength of current
would affect an object protected by an intervening sheet half an inch