Изображения страниц
PDF
EPUB

a

is infirm was in the end the fruit of Woodrow Wilson's immaculate conception of a new world order. It was a great statesman who with fearlessness and eloquence proclaimed a new charter of liberty for a stricken world; but it was a timid politician who assisted in the forging of new chains for sorrowing humanity. So at least it appears to a contemporary observer. In Woodrow Wilson we seem to have all the elements of a classic tragedy: a truly great man with a truly noble vision and purpose involved in a gigantic catastrophe, helpless to avert or to change it through some fatal flaw of character or some gross error in conduct. What a theme for a Sophocles or a Shakespeare! Woodrow Wilson the statesman, such perhaps will be the verdict of history, went down to defeat slain by Woodrow Wilson the politician.

J. L.

WHAT WE KNOW ABOUT EARTHQUAKES

Professor H. F. Reid, of Johns Hopkins University, summarizes our knowledge of earthquakes in a recent number of the Proceedings of the National Academy of Sciences as follows:

Nearly all earthquakes are due to the sudden fracture of the rock of the earth's crust, which has been strained by slow earth movements beyond its strength. Strong vibrations are set up at the fractured surface at the time of the fracture, just as vibrations are set up whenever any solid is broken. The earth consists of solid material, which is necessarily elastic, and therefore these vibrations are transmitted through it as elastic waves. There are two kinds of elastic waves : normal waves, where the movement is in the direction of propagation, and transverse waves, where the movement is at right angles to the direction of propagation. These two kinds of vibration advance with different velocities. Their velocities near the earth's surface are about 7 and 4 kms. per second, respectively; but the deeper they penetrate below the surface the faster they go. Therefore, from the characteristics of elastic waves their paths are curved and concave upwards. These important results have been obtained by a study of the time necessary for the two types of waves to pass from the place of their origin to stations at different distances, where delicate instruments are installed which record the time of their arrival. It may seem remarkable that the paths followed by the waves and the velocity in different parts of the paths could be determined merely from the time required to arrive at a number of places on the earth's surface; but, by the help of some rather abstruse mathematics, it can be done. One interesting conclusion which can be drawn from the passage of the transverse waves through the body of the earth is that the earth is a solid and not liquid sphere; for transverse waves can be transmitted only by solid substances.

There are other waves which are transmitted along the surface of the earth; they must be started in some way when the body waves, mentioned above, arrive at the surface, but we do not know just how near the origin their starting place is.

In many instances submarine earthquakes give rise to great water waves, which have been known to travel from one side of the Pacific Ocean to the other. It has been the general belief that the first indication of these waves along a coast is marked by the withdrawal of the water; and the great elevated wave follows. Although this order is certainly frequent, it is not general, and in many cases the elevated wave is first to appear.

This is a very summary sketch of what has been learned about earthquakes in the comparatively short time that they have been systematically studied; but it will serve as a basis from which to point out the problems which are now pressing for solution.

[graphic][subsumed]
[blocks in formation]

(TENZONE DI FONTANE) Fountain of Rosello! There are twelve throats that spill your crystal song (Praise of the fairest must to you belong), Twelve gushing throats there are that pour your pain, But in my heart the anguish must remain.

Fountain of Ploaghe!
From the cool rock your living waters spring
(Fame of the purest must about you cling),
You drop in bounty down the mountain side,
But in my heart the hot thirst must abide.

Fountain of Rosello!
The marble throats that spill your waters free
Can give no drop to me.

Fountain of Ploaghe!
The rocky bosom where your waters live
To me no drop can give.

Fountains of earth, you have no mossy brink,
No crystal pool where Love may kneel and drink
A draught to quench the fire
Of his unspent desire !

« ПредыдущаяПродолжить »