e to
darken the light colors of the room, not being heated sufficiently to
combine with the oxygen. This product of the combustion of gas (free
carbon) might be regarded as rather wholesome than otherwise (as its
nature is that of an absorbent) were it not the worst kind of dust to
breathe--in fact, clogging the lungs to suffocation. In vapor gas--made
at low heat--the carbon is in a large degree only mechanically mixed
with the hydrogen, and is liable, especially in cold weather, to be
deposited in the pipes. This leaves only a very poor, thin gas, mainly
hydrogen, which burns with a pale blue flame, as seen in cold spells in
winter. High heats and short charges in the retorts of the manufactory
give a purer gas and a larger production. Gas made at high heat will
reach the consumer in any weather very nearly as rich as when it leaves
the gas-holder; for, thus made, the hydrogen and carbon are chemically
combined, instead of the hydrogen merely bearing a quantity of
carbon-vapor mechanically mixed and liable to deposit with every
reduction of temperature. To relieve the atmosphere of the gases and
vapors proceeding from combustion is, of course, the purpose of
ventilation. The sulphuric acid gas and ammonia will be largely in
combination with the water-vapor, which also proceeds from combustion,
so that all will be got rid of together. The vaporization of libraries
to counteract the excessive dryness (or drying, rather) which causes
leather bindings to shrink and to break at the joints, would be of
doubtful utility, since it might only serve to carry into the porous
leather still more of the gases just mentioned. The action of both
sulphuric acid and ammonia is, undoubtedly, to destroy the fibre of
leather, so that it crumbles to meal or falls apart in flakes.

"In a very interesting paper read by Professor William R. Nichols of the
Massachusetts Institute of Technology before the American Association of
Science at its Saratoga meeting in 1879, the results of many analyses of
leather bindings were given, showing the presence of the above-named
substances in old bindings in many times greater quantity than in new.
Still, their presence did not prove them to be the cause of the decay;
and Professor Nichols proposes to ascertain the fact by experiments
requiring some years for demonstration.

"In the hope of deciding the question with reasonable certainty at once,
I have made careful examinations of the books in the three