roof in like manner to the raising of the kettle-lid? Without dilating
on this part of the subject, we mention it as a possible cause of minor
explosions--doubtless to become better known in future. It may even be
that explosions happening from steam acting in close spaces may have
been attributed to gunpowder, or to niter and other salts, separate, but
suddenly caused to combine in chemical reaction.--_American Exchange and
Review._

* * * * *




CARBON.--SYMBOL C.--COMBINING WEIGHT 12.

By T.A. POOLEY, B.Sc., F.C.S.


This element, which next deserves our attention, is one of great
importance and wide distribution; it occurs in nature in both the free
and the combined states, and the number of compounds which it forms with
other elements is very large. Unlike the previous elementary bodies we
have studied, carbon is only known to us in the solid form when
free, although many of its combinations are gaseous at the ordinary
temperature and pressure. Carbon is known to exist in several different
physical states, thus illustrating what chemists call _allotropism_,
which means that substances of identical chemical composition sometimes
possess altogether different outward and physical appearances. Thus the
three states in which pure carbon exists, viz., diamond, graphite, or
plumbago, and charcoal are as different as possible, and yet chemically