strata of littoral and estuary origin, to which the name Potomac formation has been applied. These deposits are only a few hundred feet thick, and, though frequently covered from sight, seem to be continuous from New Jersey to Mississippi. Invertebrate fossils are rare, but large collections of fossil plants have been found in the Potomac region. The best authorities recognize several of these fossils as Jurassic. Briefly, then, the Mesozoic of the Atlantic coast region consists of a probable representation of the Upper Trias of Europe, a possible one of the Upper Jura, a probable slight one of the Middle Cretaceous, and a practically certain representation of a large part of the Upper Cretaceous, with a hiatus between the latter and the Eocene. The speaker advocated a system of classification more suited to this country than the European one. The time has come when North American geologists can and ought to hold a commanding position in this matter.
Olives and their Oil.—The olive has been cultivated in the regions of the Mediterranean coasts from time immemorial. Olive-oil there takes the place of butter. Spain has about 3,000,000 acres in olives, Italy 2,250,000, and France about 330,000 acres. Forty-five varieties of the fruit are described. The tree occasionally grows to be sixty feet high, and twelve feet in circumference of trunk. The varieties differ in the nature of the wood, the foliage, and the quality and shape of the fruit. The fruit is mild, or sharp, or bitter; and the oils differ likewise; so that a pure olive-oil may be unfit for purposes of food, and only fit for greasing machinery and making soap. The green, unripe olives, having had the bitter taste extracted with salt, are preserved in vinegar with spices. The ripe olives are gathered in the fall, when they are as large as common plums. They are of dark-green color, and the pit, now become a hard stone, contains a savory kernel. The flesh is spongy, and its little cells are filled with the mild oil, which runs out at the least pressure. The finest oil is the virgin oil which is made by collecting the freshly gathered olives in little heaps, and letting them press the oil out by their own weight. It is clear, and has a delicate, nutty taste, with little or no odor. When the fruits cease to give the oil by themselves, they are pressed with small millstones, yielding an oil which is also clear and has a pleasant taste. The olives, still rich in oil, are next put in sacks, boiling water is poured over them, and they are pressed once more. The oil gained by this process is yellowish-green, and has a sharp taste and an unpleasant smell. At Marseilles the olive-oils are classed into manufacturing oils for burning, greasing machinery, and soap-making; refined oil; oil from the pulp or husks, and table or edible oil. The last is superfine, fine, half fine, and ordinary. The table oil is refined by allowing it to run through layers of thin sheets of wadding into tin perforated boxes. The wadding absorbs all the thick particles, and leaves the oil clear and tasteless. The olive crop is variable and uncertain, and is seldom profitable more than once in six or eight years.
Avogadro.—According to a sketch published by Prof. Hugo Schiff, of Florence, in the "Chemiker Zeitung," Amadeo Count Avogadro, son of the magistrate Filippo Vercellone, was born in Turin, August 9, 1776. He studied jurisprudence at the Turin University, became Doctor of Laws on March 16, 1796, and then held a position under the Government till 1806, when he began his scientific career. In physics he was self-taught, and obtained a subordinate position in the Collegio delle Provincie in Turin, which was then and still is a richly endowed department of the Turin University. On November 7, 1809, he became Professor of Physics at the Gymnasium in Vercelli. In 1820 he was elected Professor of Mathematical Physics at the Turin University. Later this chair of instruction was abolished, and Avogadro resumed the practice of law. He was, however, reinstated in his chair through the influence of Charles Albert, and remained at the university till 1850, when he retired on account of old age and ill health. He died at Turin, July 9, 1856, at the age of eighty years. Avogadro was but little known in Italy and unknown in foreign countries. He shared with Charles Gerhard, who died in the same year, August 19, 1856, the same fate. It was only after death that their great and important contributions to science found recognition.