possible that
some other efficient light-source may be more effective in forcing the
growth of plants. These and many other factors must be carefully
determined before judgment can be passed on the efficacy of artificial
light in reducing the cost of living in this direction. Certainly,
artificial light has been shown to increase the growth of plants and it
appears probable that future generations at least will find it
profitable to use the efficient light-producers of the coming ages in
this manner.

Many other instances could be cited in which artificial light is very
closely associated with the cost of living. Overseas shipment of fruit
from the Canadian Northwest is responsible for a decided innovation in
fruit-picking. In searching for a cause of rotting during shipment it
was finally concluded that the temperature at the time of picking was
the controlling factor. As a consequence, daytime was considered
undesirable for picking and an electric company supplied electric
lighting for the orchards in order that the picking might be done during
the cool of night. This change is said to have remedied the situation.
Cases of threshing and other agricultural operations being carried on at
night are becoming more numerous. These are just the beginnings of
artificial light in a new field or in a new relation to civilization.
Its economic value has been demonstrated in the ordinary fields of
lighting and these new applications are merely the initial skirmishes
which precede the conquest of new territory. The modern illuminants have
been developed so recently that the new possibilities have not yet been
established. However, artificial light is already a factor on the side
of the people in the struggle against the increasing cost of living, and
its future in this direction is still more promising.

XIX

ARTIFICIAL LIGHT AND CHEMISTRY

Some one in an early century was the first to notice that the sun's rays
tanned the skin, and this unknown individual made the initial discovery
in what is now an extensive branch of science known as photo-chemistry.
The fading of dyes, the bleaching of textiles, the darkening of silver
salts, the synthesis and decomposition of compounds are common examples
of chemical reactions induced by light. There are thousands of other
examples of the chemical effects of light some of which have been
utilized by mankind. Others await the development of more efficient
light-sources emitting g