“In the life of Apollonius Tyanaeus, written by Philostratus 1500 years ago, we find, in reference to the Indians called Oxydra:  These truly wise men dwelled between the rivers Hyphasis and Ganges; their country Alexander the Great never entered, being deterred, not by fear of the inhabitants, but, as I suppose, by, religious considerations, for had he passed the Hyphasis, he might doubtless have made himself master of the country all round him; but their cities he could never have taken, though he had led a thousand as brave as Achilles or ten thousand such as Ajax to the assault.  For they come not out into the field to fight those who attack them; but these holy men, beloved of the gods, overthrow their enemies with tempests and thunder-bolts shot from their walls.

“It is said that Egyptian Hercules and Bacchus (Dionysius), when they overran India, invaded this people also, and having prepared warlike 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.