now used for making the oxides of zirconium, lanthanum, cæsium, etc., to be employed for manufacturing purposes. A considerable number of cases of exceptional discoveries of gems of rare value are recorded, but they are so scattered as not to admit of grouping either by kind or place. Among the notable collections of gems in the United States mentioned by the author, are the three hundred and thirty-one antique gems of the late Rev. C. W. King, of England, which have been presented to the Metropolitan Museum of Art; Mr. Maxville Somerville's collection of fifteen hundred specimens of antique jewel-carving art, now on loan in the Metropolitan Museum; the Rev. Dr. W. Hayes Ward's three hundred ancient Babylonian, Persian, and other cylinders, now the property of the museum; the gem collection bequeathed by Dr. Isaac Lea to his daughter; and the series of precious stones, including about one thousand specimens, which, though not expensive, are the finest in the United States from an educational point of view, belonging to the National Museum. Mr. Kunz also gives some interesting fashion-notes about precious stones. They fluctuate in favor. Amethysts and cameos, much sought for ten years ago, are now thrown out. Rubies, already very high, are all the time rising. Topaz is not in demand. Coral is going out, while the popularity of amber is increasing. The use of Brazilian pebbles has decupled since 1878. The rare stones known as "fancy stones," which were formerly kept only as specimens, are now looked upon as articles of trade, and as part of the normal jeweler's stock. Mr. Kunz, as agent of Tiffany & Co., had a fine collection of North American precious and ornamental stones at the Paris Exposition, of which we have published a laudatory notice by "La Nature." It included three hundred and eighty-two specimens.
Botany as a Disciplinary Study.—Botany is recommended as a disciplinary study by Mr. Gerald McCarthy. It is much in its favor that the objects with which it deals are convenient of access and full of interest. Among the other advantages that it offers are the adaptation of the study of plants to the cultivation of the æsthetic faculties; to training the mind to habits of close observation and discriminating judgment, orderly arrangement, and the "logic of systemization"; its presenting the phenomena of life in its least complicated manifestations; plants offering better opportunities for thorough study than is practicable with minerals and animals; the usefulness of the study as a recreation and mental tonic; and the inexhaustible field for research which it offers. If some object that the technical names are hard, "at the beginning it will serve just as well to use the common vernacular name, or even invent names for one's self. The name is the least important thing one can learn about a plant, and it is not wise for the beginner to exhaust his time and patience in trying to choose the most proper of several possible and equally unintelligible names. Rather he should seek to group the specimens around common types, thus learning for himself the philosophy of the natural system." But the scientific name must eventually be learned, and it will come easier after the student has observed well for himself. For young pupils, and older ones who are unfamiliar with Latin, Miss Youmans's "First Book in Botany" is recommended as the best manual to begin with. It will lead up to the more advanced works. But more useful than any book is the student's field outfit, of lenses and knives, needles and trowel, and air-tight specimen-box.
Causes of Unhealthiness in Large Cities.—The mere age of London, said Dr. G. V. Poor, in a lecture at the Sanitary Institute, was one of the reasons why it became unwholesome. Roman London was buried deeply among rubbish of all kinds, much of which was putrescible, and therefore a source of danger in the soil. Ancient London was well placed and magnificently supplied with water through the Thames and many smaller streams. All the smaller streams had become disgracefully foul, "and for very shame had been covered over." That mediæval London was very unhealthy, a perfect fever-den, there could be no doubt. The causes of the enormous mortality lay in the marshy, undrained soil, fouled with refuse of every kind; in the filthy state of the unpaved city, and a perfectly swinish condition of the houses of the lower
