cian ascendancy the streets of Athens and of some other Hellenic
cities were lighted by night. The material of such illumination was
oil derived either from animals or from vegetable products, such as
the olive. In the forms of Greek lamps we have an example of artistic
beauty not surpassed or equaled in modern time; but the mechanical
contrivance for producing the light was poor and clumsy.

Rome lighted herself artificially. She had her lamps and her torches
and her chandeliers, as we see in the relics of Herculaneum and
Pompeii. A Roman procession by night was not wanting in brilliancy and
picturesqueness. The quality of the light, however was poor, and there
was always a cloud of smoke as well as of dust hovering about Roman
processions and triumphs.

The earlier Middle Ages improved not at all; but with the Renaissance
there was an added elegance in the apparatus of illumination.
Chandeliers were made in Italy, notably in Venice, that might rival in
their elegance anything of the present age. The art of such products
was superior; but the old barbaric clumsiness was perpetuated in the
mechanical part. With the rise of scientific investigation under the
influence of inductive philosophy, all kinds of contrivances for the
production of artificial light were improved. The ingenuity of man was
now turned to the mechanical part, and one invention followed another
with a constant development in the power of illumination.

We can but remember, however, that until the present age many of the
old forms of illuminating apparatus have been retained. In the ruder
communities such things may still be seen. Civilization in its
progress from east to west across our continent followed a tallow
candle. The light of it was seen by night through the window of the
pioneer's cabin. The old forms of hanging lamps have hardly yet
disappeared from the advance posts of the marching column. But
meanwhile, other agencies have been discovered, and other forms of
apparatus invented, until the branch of knowledge relating to
illumination has become both a science and an art.

Within the memories of men still living, a great transformation has
occurred. Animal oils have virtually ceased to be employed as the
sources of light. The vegetable world is hardly any longer drawn upon
for its products. Already before the discovery of petroleum and its
multifarious uses the invention by chemical methods of illuminating
materials had begun. Many kinds