The sounds, too, which so frequently accompany earthquakes are likewise simply results of this division of the waves and their escape into the air, for we perceive wave motions in the air as sound. The admirable delicacy of our sense of hearing is here manifested, for seismic movements are not rarely perceptible, or heard, as air waves, which we can not perceive as movements of the ground. Earthquake thunder is caused, like storm thunder, by shocks to the air, of which we hear the nearest and latest first, and the farthest and earliest last. The different tone shades of the earthquake sound depend upon their various sources, as from small, sharp fragments, clinking, rattling, and humming; from sand and earth, dull rumbling; from trees, whistling, etc. The echo in ravines not rarely operates to add strength to them. Earthquake sounds that seem to come out of the air from above are caused by earthquake waves reaching us by way of trees, houses, etc.; the different directions and degrees of force which they seem to indicate in different houses or in different rooms of the same house are explainable by the different elasticity conditions of the houses and rooms. But not the most insignificant conclusion can be drawn from these sounds concerning the nature and causes of earthquakes. It is important to emphasize this fact, for errors have often originated in conclusions drawn from such things.—Translated for the Popular Science Monthly from the Deutsche Rundschau.
Examples of a race of curiously protectively colored mice which inhabit the sandy island, the North Bull, in the Bay of Dublin, were exhibited by Dr. H. Lyster Jameson in the Zoölogical Section of the British Association. A considerable percentage of them were distinctly lighter hued than the ancestral type of house mouse, though every possible gradation occurred between the typical house mouse and the palest examples. The speaker regarded the marked predominance of sand-colored specimens as due to the action of natural selection. The hawks and owls which frequent the island, and are the only enemies the mice have to compete against, most easily capture the darkest examples, or those that contrast most strongly with the color of the sand. Thus a protectively colored race is becoming established. The island came into existence only about a hundred years ago. Consequently it is possible to fix a time limit within which the sandy-colored race has been evolved. Its evolution also, as Professor Poulton observed in his comment on Dr. Jameson's paper, gives additional evidence to that afforded by the shore crabs described by Professor Weldon in his presidential address to the section, that the transmutation of species is not necessarily so slow as to be indiscernible.
A SHORT HISTORY OF SCIENTIFIC INSTRUCTION[33]
By J. NORMAN LOCKYER, K. C. B., F. R. S.
The two addresses by my colleagues, Professors Judd and Roberts-Austen, have drawn attention to the general history of our college and the details of one part of our organization. I propose to deal with another part, the consideration of which is of very great importance at the present time, for we are in one of those educational movements which spring up from time to time and mold the progress of civilization. The question of a teaching university in the largest city in the world, secondary education, and so-called technical education are now occupying men's minds.
At the beginning it is imperative that I should call your attention to the fact that the stern necessities of the human race have been the origin of all branches of science and learning; that all so-called educational movements have been based upon the actual requirements of the time. There has never been an educational movement for learning's sake; but of course there have always been studies and students apart from any of those general movements to which I am calling attention; still we have to come down to the times of Louis Quatorze before the study of the useless, the même inutile, was recognized as a matter of national concern.
It is perhaps the more necessary to insist upon stern necessity as being the origin of learning, because it is so difficult for us now to put ourselves in the place of those early representatives of our race that had to face the problems of life among conditionings of which they were profoundly ignorant: when night meant death; when there was no certainty that the sun would rise on the morrow; when the growth of a plant from seed was unrecognized; when a yearly return of seasons might as well be a miracle as a proof of a settled order of phenomena; when, finally, neither cause nor effect had been traced in the operations of Nature.