. Elements of geology : a text-book for colleges and for the general reader. Geology. EARTHQUAKES, 121 The vorticose motion in sncli cases is probably not real, but only ap- parent. But tliere are other cases of undoubtedly real vorticose motion; as, for example, straight rows of trees changed into interrupted zigzags by fissures and displacement. All such cases of real hoisting are prob- ably explicable on the principle of concurrence and interference of loaves. If two systems of waves of any kind meet each other, there will be points of concurrence where they re-enforce each other, and point
. Elements of geology : a text-book for colleges and for the general reader. Geology. EARTHQUAKES, 121 The vorticose motion in sncli cases is probably not real, but only ap- parent. But tliere are other cases of undoubtedly real vorticose motion; as, for example, straight rows of trees changed into interrupted zigzags by fissures and displacement. All such cases of real hoisting are prob- ably explicable on the principle of concurrence and interference of loaves. If two systems of waves of any kind meet each other, there will be points of concurrence where they re-enforce each other, and points of interference where they destroy each other. Suppose, for instance, a system of water-waves, represented by the double lines i, i (Fig. 102), running in the direction o #, strike against a wall, w w : the waves would be reflected in the direction c c, and are represented by the single lines r, r. Then, if the lines represent crests, and the intervening space the troughs, at the places marked with crosses and dots there would be concurrence, and therefore higher crests and deeper troughs, while at the points indicated by a dash there would be inter- ference and mutual destruction, and therefore smooth water. The same takes place in earth-waves. If two systems of earth-waves meet and cross each other, we must have points of concurrence and interference in close proximity. The ground, therefore, will be thrown into violent agitation—points in close proximity moving in opposite directions (twisting). If the motion be sufficient to rupture the earth, restoration is not made by counter-twisting, and the earth is left in a disyjlaced condition. The causes of interference may be various—sometimes by the nor- mal and transverse waves combining differently so as to produce motion in different directions in contiguous places; sometimes by difference of velocity of waves, already explained, by which some overrun others, concurring and interfering; more often it is the result of ref
Size: 2378px × 1051px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectgeology, bookyear1892
