In the opinion of many learned authorities, the shaft of this column was once a portion of the Serapeum, that famous building which was both a temple of the heathen god Serapis and a vast treasure-house of ancient civilization. It has been suggested--in order to account for its omission in the descriptions of Alexandria, given by Pliny and Strabo, who had mentioned the two obelisks of Cleopatra--that the column had fallen, and that the Prefect Pompey had merely re-erected it in honor of Diocletian, and replaced the statue of Serapis with one of the Emperor--or of his horse, according to some chroniclers. This statute, if it ever existed, has now disappeared. As it stands, however, it is a singularly striking and beautiful monument, owing to its great height, simplicity of form, and elegant proportions. It reminds the spectator a little of Nelson's Column in Trafalgar Square, and perhaps the absence of a statue is not altogether to be regretted considering the height of the column, as it might suggest to the irrepressible tourists who scoff at Nelson's statue as the "Mast-headed Admiral," some similar witticism at the expense of Diocletian. With the exception of this monolith, which, "a solitary column, mourns above its prostrate brethren," only a few fragmentary and scattered ruins of fallen columns mark the site of the world-renowned Serapeum. Nothing else remains of the famous library, the magnificent portico with its hundred steps, the vast halls, and the four hundred marble columns of that great building designed to perpetuate the glories of the Ptolemies. This library, which was the forerunner of the great libraries of modern times, must not be confounded with the equally famous one that was attached to the Museum, whose exact site is still a bone of contention among antiquarians. The latter was destroyed by accident, when Julius Cæsar set fire to the Alexandrian fleet. The Serapeum collection survived for six hundred years, till its wanton destruction through the fanaticism of the Caliph Omar. The Arab conqueror is said to have justified this barbarism with a fallacious epigram, which was as unanswerable, however logically faulty, as the famous one familiar to students of English history under the name of Archbishop Morton's Fork. "If these writings," declared the uncompromising conqueror, "agree with the Book of God, they are useless, and need not be preserved; if they disagree, they are pernicious, and ought to be destroyed." Nothing could prevail against this flagrant example of a _petitio principii_, and for six months the three hundred thousand parchments supplied fuel for the four thousand baths of Alexandria. Hard by Pompey's Pillar is a dreary waste, dotted with curiously carved structures. This is the Mohammedan cemetery. As in most Oriental towns, the cemetery is at the west end of the town, as the Mohammedans consider that the quarter of the horizon in which the sun sets is the most suitable spot for their burying-places.