Something of detail on this subject cannot, I think, fail to prove interesting. Pliny mentions about thirty or forty oils as known to the ancients, of which only olive, sesame, rape seed and walnut oil--for except in one or two doubtful passages I find in this author no notice of linseed oil--appear to have been used in such quantities as to have had any serious importance in the carrying trade. At the present time, the new oils, linseed oil, the oil of the whale and other largeo marine animals, petroleum--of which the total consumption of the world in 1871 is estimated at 6,000,000 barrels, the port of Philadelphia alone exporting 56,000,000 gallons in that year--palm-oil recently introduced into commerce, and now imported into England from the coast of Africa at the rate of forty or fifty thousand tuns a year, these alone undoubtedly give employment to more shipping than the whole commerce of Italy--with the exception of wheat--at the most flourishing period of the Roman empire. [Footnote: A very few years since, the United States had more than six hundred large ships engaged in the whale fishery, and the number of American whalers, in spite of the introduction of many now sources of oils, still amounts to two hundred and fifty. The city of Rome imported from Sicily, from Africa, and from the Levant, enormous quantities of grain for gratuitous distribution among the lower classes of the capital. The pecuniary value of the gems, the spices, the unguents, the perfumes, the cosmetics and the tissues, which came principally from the East, was great, but these articles were neither heavy nor bulky and their transportation required but a small amount of shipping. The marbles, the obelisks, the statuary and other objects of art plundered in conquered provinces by Roman generals and governors, the wild animals, such as elephants, rhinoceroses, hippopotami, camelopards and the larger beasts of prey imported for slaughter at the public games, and the prisoners captured in foreign wars and brought to Italy for sale as slaves or butchery as gladiators, furnished employment for much more tonnage than all the legitimate commerce of the empire, with the possible exception of wheat. Independently of the direct testimony of Latin authors, the Greek statuary, the Egyptian obelisks, and the vast quantities of foreign marbles, granite, parphyry, basalt, and other stones used in sculpture and in architecture, which have been found in the remains of ancient Rome, show that the Imperial capital must have employed an immense amount of tonnage in the importation of heavy articles for which there could have been no return freight, unless in the way of military transportation. Some of the Egyptian obelisks at Rome weigh upwards of four hundred tons, and many of the red granite columns from the same country must have exceeded one hundred tons. Greek and African marbles were largely used not only for columns,