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Page:Popular Science Monthly Volume 48.djvu/953

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While illustrating glacier movements to the British Association, Prof. W. J. Sellers said that pitch and glacier ice strikingly resemble each other in behaving as solids or liquids, according to circumstances. On the sudden application of force they are very brittle, but behave as fluids when subjected to gradual pull and pressure. Hence it is possible to employ pitch in the construction of working models of glaciers, in order to get an insight into those internal movements of real glaciers which are beyond the reach of actual observation. The study of glacial deposits has shown that many erratic bowlders are transported during the Glacial period from lower to higher levels hundreds of feet and left stranded on the rocky flanks of mountains. This standing difficulty in the way of physical theories of glacial movement has been explained by the study of pitch models, by means of which it is found that the lower layers of material, in approaching an obstacle, are carried up in an ascending current. The inference, which is confirmed by natural facts, is that similar movements would certainly take place in actual glaciers. Further, a glacier sometimes overrides its terminal without disturbing it, and in an experiment performed by the author this was exemplified, for pitch flowed for several months over a ridge of loose material without carrying a particle of it away.

Believing that the longest-tongued bees are the most profitable—they being able to extract honey from the greatest depths within the flowers yielding it—MM. Charton and Legros have devised methods for measuring bees' tongues. M. Charton's apparatus consists of a box covered with metallic netting, and having the bottom slightly inclined. On this bottom is spread a sweetened liquid which the bees can reach only by passing their tongues through the meshes of the netting. The hive whose bees can suck farthest down the inclined bottom is preserved as a stock for reproduction. M. Legros uses a receiver closed by a sheet of perforated tin plate, from which the sweetened liquid is fixed at carefully adjusted distances. M. Legros finds that the tongues of common unselected bees are 6·5 millimetres long, while the black French bees can extract sirup at a maximum distance of 9·2 millimetres. The tongues of the best American bees reach to 8·73 millimetres.

The domestic weeds of ancient civilization, the roadside weeds and the cornfield weeds, says W. B. Hemsley, in a recent issue of Knowledge, have accompanied man in his most distant wanderings, and in many instances have developed increased vigor, and a power of colonization unsurpassed by man himself. In some instances the reproduction and spread of these weeds are so rapid as to become a great scourge to agriculture, overrunning and destroying crops almost as effectually as swarms of locusts, and laws have been framed making it compulsory on farmers to keep their land free of these prolific strangers. During the last three or four years the so-called Russian thistle (Salsola kali, var. tragus) has been occupying the serious attention of the farmers of the Eastern and Central States of North America. Thousands of square miles are infested, and the loss resulting therefrom in 1892 was estimated to exceed two million dollars.

Prof. John Miln's report of eight thousand three hundred and thirty-one earthquake shocks recorded in Japan, in which the position of the origin of each shock and the extent of country disturbed by it are described, deals further with the propagation of earthquake disturbances on the surface of the earth, and possibly through it. Elastic gravitational waves travel in Japan, or thence to Europe, as surface waves at a rate of three thousand metres per second, increasing in period as they proceed; these are the earthquake disturbances proper. Preceding them in Japan are minute vibrations, and these apparently travel to Europe at a rate of from about eight thousand to ten thousand metres per second. It is suggested that they may travel, not along the surface, but through the mass of the earth, by some path, straight or curved; and that with a speed greater than would be expected if the globe were of glass or steel. Dr. Rebeun Paschnitz is of the opinion that if such be the case they may throw light on the internal structure of the globe.