compass, and, after the ravages of three centuries and three conquerors, still more than eighty feet in height; there were still the ruins of the temple of cloud encompassed Bel, on its top was planted the observatory wherein the weird Chaldean astronomers had held nocturnal communion with the stars; still there were vestiges of the two palaces with their hanging gardens in which were great trees growing in mid-air, and the wreck of the hydraulic machinery that had supplied them with water from the river.  Into the artificial lake with its vast apparatus of aqueducts and sluices the melted snows of the Armenian mountains found their way, and were confined in their course through the city by the embankments of the Euphrates.  Most wonderful of all, perhaps, was the tunnel under the river-bed.

Effect on the Greek army.  If Chaldea, Assyria, Babylon, presented stupendous and venerable antiquities reaching far back into the night of time, Persia was not without her wonders of a later date.  The pillared halls of Persepolis were filled with miracles of art—­carvings, sculptures, enamels, alabaster libraries, obelisks, sphinxes, colossal bulls.  Ecbatana, the cool summer retreat of the Persian kings, was defended by seven encircling walls of hewn and polished blocks, the interior ones in succession of increasing height, and of different colors, in astrological accordance with the seven planets.  The palace was roofed with silver tiles, its beams were plated with gold.  At midnight, in its halls the sunlight was rivaled by many a row of naphtha cressets.  A paradise—­that luxury of the monarchs of the East—­was planted in the midst of the city.  The Persian Empire, from the Hellespont to the Indus, was truly the garden of the world.

Effects on the Greek army.  I have devoted a few pages to the story of these marvelous campaigns, for the military talent they fostered led to the establishment of the mathematical and practical schools of Alexandria, the true origin of science.  We trace back all our exact knowledge to the Macedonian campaigns.  Humboldt has well observed that an introduction to new and grand objects of Nature enlarges the human mind.  The soldiers of Alexander and the hosts of his camp-followers encountered at every march unexpected and picturesque scenery.  Of all men, the Greeks were the most observant, the most readily and profoundly impressed.  Here there were interminable sandy plains, there mountains whose peaks were lost above the clouds.  In the deserts were mirages, on the hill-sides shadows of fleeting clouds sweeping over the forests.  They were in a land of amber-colored date-palms and cypresses, of tamarisks, green myrtles, and oleanders.  At Arbela they had fought against Indian elephants; in the thickets of the Caspian they had roused from his lair the lurking royal tiger.  They had seen animals which, compared with those of Europe, were not only