Page:Popular Science Monthly Volume 20.djvu/591

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are not in Bight during the recitation. In learning the lesson, books are not used, for, if they are used, no books will contain a quarter of what the pupil may see for himself." And the professor goes on to describe the particular features of his method in a manner that makes most interesting reading.

The International Committee of the Red Cross (Geneva Convention) has offered prizes for three essays, designed to constitute a series, on "The Art of improvising Means for assisting the Wounded and Sick of Armies." The three essays will relate, respectively, to methods of treatment, means of transportation, and the improvisation of an ambulance or a field-hospital. The consideration of the subjects must be limited to improvisation, and have no reference to fore-prepared means of assistance. The processes suggested should be illustrated by designs when practicable; and the essays should be full, scientific works, not manuals, and should describe expedients that have been tried and tested for practicability. The papers, which may be in English, German, or French, should be sent in before the first day of April, 1883. The awards will be made by an international jury, and will include a prize of five hundred dollars for the best essay on each of the three topics, if worthy, and one hundred dollars to the unsuccessful competitors.

Two views are held regarding the relative age of the copper-bearing traps of Keweenaw Point, Lake Superior, and the Eastern sandstone: one, that the traps and sandstone are of the same age; the other, that the traps are an earlier formation (pre-Palæozoic), and the Eastern sandstone a later one (Palæozoic). Mr. M. E. Wadsworth, having carefully examined the relative position of the two rocks, finds that the Eastern sandstone underlies the trap conformably, "that is, as conformably as a bed can underlie a lava which has flowed over it," and that, therefore, it must be older in order of time, but of the same geological age with the copper-bearing rocks. Hence, the "Keweenawan series," which has been projected upon the theory that the copper-bearing rocks are the older ones, has no foundation. The balance of evidence in regard to the absolute age of the rocks appears to be with the views of Messrs. Whitney and Foster, that they are of the Potsdam age.

Seubert having observed that, in the periodic systems of classification of the metals of Meyer and Mendelejeff, platinum comes before gold, while the received atomic weight, 196·7 to 197·8, puts it after that metal, recently undertook the revision of its atomic weight. Having obtained the pure metal, by Schneider's method, he then, with pure potassium chloride and pure ammonium chloride, prepared the double salts by four methods. The mean value of eight experiments, corrected and reduced to a vacuum, gave 194·34050 as the atomic weight of platinum.

The Peabody Museum of American Archæology and Ethnology has been forced for lack of means to suspend the explorations it had undertaken. Its last report, however, shows that it has done much good work and made many valuable acquisitions. The largest gift received during the year was a collection of Peruvian relics of all kinds, particularly rich in fabrics and garments, received from Dr. W. Sturgis Bigelow, which, added to the other Peruvian collections, makes this department an imposing one. Dr. Flint has brought from Nicaragua many copies of inscriptions on rocks and caves. Mr. Edwin Curtis has procured many thousand specimens, which are recorded in 1,431 entries, from the mounds of Eastern Arkansas. Numerous other hardly less important acquisitions arc noticed. The museum has in press a work by Dr. Abbott, of Trenton, New Jersey, on "Primitive Industry, or Illustrations of the Handiwork in Stone, Bone, and Clay, of the Native Races of the Northern Atlantic Seaboard of America."

Professor Dufour has reported to the Helvetic Society of Natural Sciences an interesting observation of what he considers a new proof of the roundness of the earth, in the deformation of images produced on large surfaces of calm water. It may often be witnessed on the Lake of Geneva, and in the case of ships some miles distant at sea.

Professor M. E. Wadsworth, of Cambridge, Massachusetts, recently expressed the opinion, founded on his observations in the region, that the amygdaloid cavities and veins in the Keweenaw Point district of Lake Superior had been filled, by the action of water percolating through the rocks, with mineral matter derived from the adjacent rock. Professor J. D. Dana traversed his view, holding that all changes in the rocks took place before the rocks lost their original heat, and were brought about by means of the moisture inclosed at the time of the eruption, acting generally in the vaporized state. Professor Wadsworth has reiterated his views, with a statement of his reasons for adhering to them, before the Boston Society of Natural History. He claims respect for them because they are derived from personal knowledge of the facts, while Professor Dana's views depend on the observations of others. The discussion involves the question of the extent to which water can permeate rocks.