Page:Popular Science Monthly Volume 27.djvu/146

134 no trace of them upon an exhaustive search. He concludes that the animals must wander farther from their breeding-grounds than is supposed, or else must dig far deeper into the earth than to six or eight inches, as stated by Holbrook and De Kay.

Effect of Earthquakes on Buildings.—Mr. John Milne, of Tokio, Japan, has published some observations of the effects of earthquakes on buildings. In regard to the relative security of buildings on low and on high ground there is no universal rule, but each small area in an earthquake-region has its peculiarities. Theory indicates that soft, marshy ground is safer, because it will act as a buffer between the shock and the building; and the Temple of Diana, at Ephesus, was located with reference to this point. But experience at Tokio and Manila has shown repeatedly that there is very little, if anything, in it; and hard, rocky strata, where the amplitude of motion is small, but the period quick as compared with the motion in the inelastic material of the plains, proved the better foundation in Jamaica in 1692, and at Lisbon in 1755. Places to be avoided are the edges of cliffs, scarps, and cuttings. Europeans fasten the foundations of their buildings firmly in the ground, and their houses are much shaken. The Japanese put their structures loosely on top of stones or bowlders, and they escape serious disturbance. Europeans and Americans build iron-bound houses to resist earthquakes, and they resist them, though they get badly shaken, as a steel box would be; but they are very expensive. The Japanese and the people of the west coast of South America build a kind of wicker-basket house—a frame house with a light roof, which lives through the earthquake like "a reed shaken by the wind." The stability of such houses depends upon their not being firmly attached to the earth, and their numerous joints admit considerable yielding, so that the earthquake-wave passes through them before they begin to show its visible effects. A cheap aseismic house would be a low frame building supported by a number of slightly concave surfaces resting on segments of stone or metal spheres in connection with the ground. Chimneys should be given a play-space around them, and not be in contact with the roof; else, since the vibrational periods of the chimney and the roof never correspond, clashes will occur between them, and a shock and overthrow result. The pitch of the roof should not be great, or the tiles or slates will be shot off; and the upper parts of all buildings should be as light as is consistent with strength.

Suggestions in School-keeping.—Mrs. H. F. Wilson, in a paper read before the Educational Association of Alabama, tells how in her school she eschewed the system of marks and statistical reports as pernicious and false, and imposed as the one rule to govern the whole school, "Do right"; and, as the real goal to be reached, excellence in everything. Incorrect sentences heard by any pupil are reported in a blunder-box, to be corrected by the school. Once a week, half an hour is devoted to the recitation of facts, drawn from the public press and other sources. Half of every holiday is given to microscopic, stereoscopic, or other instructive exhibitions. In connection with the teaching of music, information is collected concerning the old masters of music. Physical culture is attended to, and dancing is cultivated as an element of it. In this work the teacher finds infinite variety and enjoyment, and has been "filled with amazement and enthusiasm at the immense amount of work pupils did unbidden, hunting over cyclopædias and books of reference for information when the text-book was obscure or inadequate."

Source of Atmospheric Electricity.—The source of atmospheric electricity has never yet been satisfactorily indicated, although various theories have been suggested to account for it. It has been attributed to aerial friction, to combustion or oxidation, to evaporation, and to condensation, to inductive or conductive effects of the earth's electricity, to convection currents, to electrified corpuscles coming from the sun, to solar radiation, to the friction of aqueous vapor against dry air, to capillary surface-tension of water, to the production of hail, etc. Professor Tait suggests that the mere contact of the particles of vapor with the air may suffice to produce the exceedingly small potential requisite to start the effects. He