At length, after a siege of thirteen months, the hopeless Moslemah received from the caliph the welcome permission of retreat.
* The march of the Arabian cavalry over the Hellespont and through the provinces of Asia, was executed without delay or molestation; but an army of their brethren had been cut in pieces on the side of Bithynia, and the remains of the fleet were so repeatedly damaged by tempest and fire, that only five galleys entered the port of Alexandria to relate the tale of their various and almost incredible disasters.
In the two sieges, the deliverance of Constantinople may be chiefly ascribed to the novelty, the terrors, and the real efficacy of the _Greek fire_.

The important secret of compounding and directing this artificial flame was imparted by Callinicus, a native of Heliopolis in Syria, who deserted from the service of the caliph to that of the emperor.

The skill of a chemist and engineer was equivalent to the succor of fleets and armies; and this discovery or improvement of the military art was fortunately reserved for the distressful period, when the degenerate Romans of the East were incapable of contending with the warlike enthusiasm and youthful vigor of the Saracens.

The historian who presumes to analyze this extraordinary composition should suspect his own ignorance and that of his Byzantine guides, so prone to the marvellous, so careless, and, in this instance, so jealous of the truth.
From their obscure, and perhaps fallacious, hints it should seem that the principal ingredient of the Greek fire was the _naphtha_, or liquid bitumen, a light, tenacious, and inflammable oil, which springs from the earth, and catches fire as soon as it comes in contact with the air.

The naphtha was mingled, I know not by what methods or in what proportions, with sulphur and with the pitch that is extracted from evergreen firs.
From this mixture, which produced a thick smoke and a loud explosion, proceeded a fierce and obstinate flame, which not only rose in perpendicular ascent, but likewise burnt with equal vehemence in descent or lateral progress; instead of being extinguished, it was nourished and quickened by the element of water; and sand, urine, or vinegar, were the only remedies that could damp the fury of this powerful agent, which was justly denominated by the Greeks the _liquid_, or the _maritime_, fire.
For the annoyance of the enemy, it was employed with equal effect, by sea and land, in battles or in sieges.