SECTION III.
At what period Christianity was first introduced into Arabia Felix it is now impossible to determine. Many causes, however, combine to make us believe that it was long after it had been spread over the neighbouring nations.
The mountains and deserts which defended the southern Arabians from the arms of the Persian kings, presented an insurmountable obstacle to every Asiatic or European invader, and even hindered any permanent connection with the rest of the world. Before the expedition of Ælius Gallus, the peninsula had never suffered from foreign invasion.[1] Alexander is indeed said to have contemplated the reduction of Arabia Felix; the fleet of Nearchus was preparing to assist the expedition by sea,[2] and the Macedonian army would perhaps have marched along the rich plains of the Euphrates, which opened to the odoriferous regions of Yaman;[3] but these designs were terminated by the death of their projector. The Roman army under Ælius Gallus seems to have
