engines, attempted to conquer them. They made no show of resistance, but
upon the enemy's near approach to their cities they were repulsed with
storms of lightning and thunder hurled upon them from above."

May we not here have the original of the Greek fire, that was in its day
so celebrated and so destructive?

Beginning then at the period of Geber, about 776 A.D., let us try to
work backwards and trace, if we can, the progress of chemical knowledge
down the stream of time.

While the Western Roman Empire had fallen, the Eastern still held its
sway as far as the rivers Tigris and Euphrates, and continued the
contest with the Persian power for the supremacy in Asia. At this time
the various creeds and beliefs of the Arabian tribes--which had been
much influenced by the settlement amongst them of Jews who had been
dispersed at the time of the destruction of Jerusalem, and many of the
sects of Christians who had been driven from the Roman empire by the
more orthodox--were deeply stirred by the new doctrine of Islam,
preached by Mahomet, A.D. 622, proclaiming the Koran as the rule of
life, and the destruction of the ancient Arabian worship of the stars
and sun and moon.

The religion of "the one God and Mahomet his prophet" took deep root,
and the injunction to pursue the unbelieving with fire and sword was
followed out with such unrelenting vigour that, within less than a
century from the death of Mahomet, the Arabian power had extended its
sway amongst nearly every tribe and nation that had owned the rule of
the Roman or Persian empires, and had reached from Spain to India, from
Samarcand to the Indian Ocean.

Egypt and Syria were conquered between A.D. 632-39, and Persia about
A.D. 632-51. Their attempts to take Constantinople by siege failed both
in A.D. 673 and 716. But they were more successful on the African shores
of the Mediterranean, which they swept along till they crossed the
Straits of Gibraltar and entered Spain in A.D. 709. Their further
progress--through France--was stayed by their defeat in a great battle
fought at Tour's, when the Gauls, under Charles Martel, forced them to
retire ultimately across the Pyrenees.

Internal dissension had, however, arisen amongst them, and the ruling
dynasty of the Ommiades was overthrown in A.D. 750 by the Abassides, who
established themselves at Damascus; and with them began that cultivation
of the arts and sciences which has thrown such lustre on the Arabian
sch