There has been a great deal of philosophical speculation on the nature of the physical causes which were called into action in the destruction of these cities, and of the plain on which they stood. These speculations, however, are to be considered as ingenious and curious rather than useful, since they can not lead to any very tangible results. We can, in fact, know nothing positive of the phenomenon except what the sacred narrative records. And yet there is a certain propriety in making philosophical inquiries in respect to the nature even of miraculous effects, for we observe in respect to almost all of the miracles recorded in the Old Testament, that, though they transcend the power of nature, still, in character, they are always in a certain sense in harmony with it. Thus the plagues which were brought upon the Egyptians, in the time of Pharaoh, are the ordinary calamities to which the country was subject, following each other in a rapid and extraordinary succession, and developed in an aggravated and unusual form. The children of Israel, in their journeys through the desert, were fed miraculously on manna. There is a natural manna found in those regions as an ordinary production, from which undoubtedly the type and character of the miraculous supply were determined. The waters of the Red Sea were driven back at the time when the Israelites were to cross it, by the blowing of a strong east wind. The blowing of a wind has a natural tendency to drive back such waters, and to lay the shoals and shallows of a river bare. The effects produced in all these cases were far greater than the causes would naturally account for, but they were all, so to speak, in the same direction with the tendency of the causes. They transcended the ordinary course of nature; still, in character, they were in harmony with its laws. It is right and proper for us, therefore, where a miraculous effect is described, to look into the natural laws related to it, for the sake of observing whatever of analogy or conformity between the causes and effects may really appear.

With reference to such analogies, the character and the physical constitution of the gorge in which the Dead Sea lies, has excited great interest in every age. The valley has been generally considered as of volcanic formation, though it is somewhat doubtful how far it is strictly correct thus to characterize it, since no signs of lava or of extinct craters appear in any part of it. The whole region, however, is subject to earthquakes, and many substances that are usually considered as volcanic productions are found here and there along the valley, especially near the southern extremity of the Dead Sea. One of the most remarkable of these substances is bitumen, a hard and inflammable mineral which has been found, from time to time, in all ages, on the shores of the sea. Some writers have supposed that the "pits," which are referred to in the passage, "And the vale of Siddim was full of slime pits," were pits of liquified bitumen or asphaltum,—that the plain of Sodom was composed in a great degree of these and similar inflammable substances—that they were set on fire by lightning from heaven or by volcanic ignition from below, and that thus the plain itself on which the cities stood was consumed and destroyed. Others suppose that under the influence of some great volcanic convulsion, attended, as such convulsions often are, by thunderings and lightnings—the brimstone and fire out of heaven, referred to in the sacred record—a sinking, or subsidence of the land at the bottom of the valley, took place; and that the waters of the Jordan overflowed and filled the cavity, thus forming, or else greatly enlarging the Dead Sea. That the waters of the sea now flow where formerly a tract of fertile land extended, seems to be implied in the passage, Gen. xiv. 3, in which it is stated that certain kings assembled their forces, "in the vale of Siddim which is the Salt Sea." The meaning is undoubtedly as if the writer had said, The armies were gathered at a place which was then the vale of Siddim, but which is now the Salt Sea.

THE DEAD SEA IN THE MIDDLE AGES.

After the destruction of Sodom and Gomorrah, the valley of the Dead Sea seemed to be forsaken of God, and to be abhorred and shunned by man, so that it remained for a great many centuries, the very type and symbol of solitude, desolation, and death. A few wild Arabs dwelt along its shores, building their rude and simple villages in the little dells that open among the mountains that border it, and feeding their camels on the scanty herbage which grew in them. Now and then some party of Crusaders, or some solitary pilgrim travelers, descended the valley from the fords of the Jordan, till they reached the sea—or looked down upon it from some commanding position among the mountains, on the eastern or western sides—and caravans or beasts of burden were accustomed to go to its southern shores to procure salt for the people of the interior. Through these and other similar channels, vague and uncertain tidings of the deadly influences of the sea and of the awful solitude and desolation which reigned around it, came out, from time to time, to more frequented regions, whence they spread in strange and exaggerated rumors throughout the civilized world. It was said that the waters of the sea filled the gloomy valley which they occupied with influences so pestiferous and deadly that they were fatal to every species of life. No fish could swim in them, no plant could grow upon their shores. It was death for a man to bathe in them, or for a bird to fly over them; and even the breezes which blew from them toward the land, blighted and destroyed all the vegetation that they breathed upon. The surface and margin of the water, instead of being adorned with verdant islands, or fringed with the floating vegetation of other seas, was blackened with masses of bitumen, that were driven hither and thither by the winds, or was bordered with a pestiferous volcanic scum; while all the approaches to the shores in the valley below were filled with yawning pits of pitchy slime, which engulfed the traveler in their horrid depths, or destroyed his life by their poisonous and abominable exhalations. In a word, the valley of the Dead Sea was for two thousand years regarded as an accursed ground, from which the wrath of God, continually brooding over it, sternly excluded every living thing. Within the last half century, however, many scientific travelers have visited the spot, and have brought back to the civilized world more correct information in respect to the natural history of the valley.

BURCKHARDT'S VISIT TO THE VALLEY OF ARABAH.

One of the earliest of the scientific travelers, to whom we have alluded, was John Lewis Burckhardt, who spent several years, in the early part of the present century, in exploring the countries around the southeastern shores of the Mediterranean Sea, under the auspices of a society established in London, called the Association for Promoting the Discovery of the Interior Parts of Africa. Burckhardt prepared himself for his work, by taking up his residence for several years in Aleppo, and in other Oriental cities, for the purpose of studying the Arabic language, and making himself perfectly familiar with the manners and customs of the people, so that in traveling through the countries which he was intending to explore, he might pass for a native, and thus be allowed to go where he pleased without molestation. He succeeded perfectly in attaining this object. He acquired the Arabic language, assumed the Arabic dress, and learned to accommodate himself, in all respects, to the manners and customs of the country. He thus passed without hindrance or suspicion where no known European or Christian would have been allowed to go.

THE VALLEY OF ARABAH.

Burckhardt explored the valley of Arabah, which extends from the Dead Sea to the Red Sea, forming, as has already been said, a southern continuation of the great Jordan gorge. He was, in fact, the first to bring the existence of this southern valley to the notice of the civilized world. The valley of the Jordan, as he describes it, widens about Jericho, where the hills which border it, join the chains of mountains which inclose the Dead Sea. At the southern extremity of the sea they again approach each other, leaving between them a valley or Ghor, similar in form to the northern Ghor, through which the Jordan flows; though the southern valley, from want of water, is a desert, while the Jordan and its tributaries make the other a fertile plain. In the southern Ghor, the rivulets which descend from the mountains are lost in the sand and gravel which form their beds, long before they reach the valley below. The valley itself, therefore, is entirely without water, and is, consequently, barren and desolate. The whole plain, as Burckhardt viewed it, presented the appearance of an expanse of shifting sands, the surface varied with innumerable undulations and low hills. A few trees grow here and there in the low places, and at the foot of the rocks which line the valley; but the depth of the sand, and the total want of water in the summer season, preclude the growth of every species of herbage. A few Bedouin tribes encamp in the valley in the winter, when the streams from the mountains being full, a sufficient supply of water is produced to flow down into the valley, causing a few shrubs to grow, on which the sheep and goats can feed.

Burckhardt and his party were an hour and a half in crossing the valley. It was in the month of August that they made the tour, and they found the heat almost intolerable. There was not the slightest appearance of a road or of any other work of man at the place where they crossed it. Still they met with no difficulty in prosecuting their journey, for the sand, though deep, was firm, and the camels walked over it without sinking. In the various journeys which Burckhardt made in these solitary regions, he carefully noted all that he saw, and copious reports of his observations were afterward published by the society in whose service he was engaged. The only instrument which he had, however, for making observations, was a pocket compass, and this he was obliged to conceal in the most careful manner from his Arab attendants, for fear of betraying himself to them. If they had seen such an instrument in his possession, they would not only have suspected his true character, but would have believed the compass to be an instrument of magic, and would have been overwhelmed with superstitious horror at the sight of it. Accordingly, Burckhardt was compelled, not only to keep his compass in concealment, as he journeyed, but also to resort to a great variety of contrivances and devices to make observations with it without being seen. Sometimes, when riding on horseback, he would stop for a moment in the way, and watching an opportunity when the attention of his companions was turned in another direction, would hastily glance at his compass unseen, covering it, while he did so, beneath his wide Arabian cloak. When riding upon a camel he could not adopt this method, for a single camel in a caravan can not be induced to stop while the train is going on. To meet this emergency, the indefatigable traveler learned to dismount and mount again without arresting the progress of the animal. He would descend to the ground, and straying away for a moment into a copse of bushes, or behind some angle of a rock, would crouch down, take out his compass, ascertain the required bearing, make a note of it secretly in a little book which he carried for the purpose in the pocket of his vest, and then returning to the camel, would climb up to his seat and ride on as before.