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