he fathers of chemistry would not have thought it possible ever to
attain.

PERIODICITY OF ATOMIC WEIGHTS

These utterly novel studies of molecular architecture may seem at
first sight to take from the atom much of its former prestige as the
all-important personage of the chemical world. Since so much depends
upon the mere position of the atoms, it may appear that comparatively
little depends upon the nature of the atoms themselves. But such a view
is incorrect, for on closer consideration it will appear that at no
time has the atom been seen to renounce its peculiar personality. Within
certain limits the character of a molecule may be altered by changing
the positions of its atoms (just as different buildings may be
constructed of the same bricks), but these limits are sharply defined,
and it would be as impossible to exceed them as it would be to build
a stone building with bricks. From first to last the brick remains a
brick, whatever the style of architecture it helps to construct; it
never becomes a stone. And just as closely does each atom retain its own
peculiar properties, regardless of its surroundings.

Thus, for example, the carbon atom may take part in the formation at one
time of a diamond, again of a piece of coal, and yet again of a
particle of sugar, of wood fibre, of animal tissue, or of a gas in the
atmosphere; but from first to last--from glass-cutting gem to intangible
gas--there is no demonstrable change whatever in any single property of
the atom itself. So far as we know, its size, its weight, its capacity
for vibration or rotation, and its inherent affinities, remain
absolutely unchanged throughout all these varying fortunes of position
and association. And the same thing is true of every atom of all of
the seventy-odd elementary substances with which the modern chemist is
acquainted. Every one appears always to maintain its unique integrity,
gaining nothing and losing nothing.

All this being true, it would seem as if the position of the Daltonian
atom as a primordial bit of matter, indestructible and non-transmutable,
had been put to the test by the chemistry of our century, and not found
wanting. Since those early days of the century when the electric battery
performed its miracles and seemingly reached its limitations in the
hands of Davy, many new elementary substances have been discovered,
but no single element has been displaced from its position as an
undecomposable body. Rather hav