PROCTOR ON EARTHQUAKES.

Temuka Leader, Issue 1180, 29 November 1883, Page 3

PROCTOR ON EARTHQUAKES.

Mr Richard A. Proctor writes as follows on the subject of earthquakes :

Since the terrible disaster at Ischia the general subject of subterranean disturbances has been much discussed in our daily and weekly papers, but for the most part without much knowledge of the conditions on which the occurrence of earthquakes and volcanic eruptions depends. It seems generally supposed that subterranean disturbances are caused by internal heat, and by the movement within the earth of great masses of compressed vapour and molten matter. This is to mistake cause and effect. Almost all forms of vulcanian disturbances are due to subterranean displacements which generate heat, not to subterranean heat by which displacements are caused. The true source of the forces at work in earthquakes and erruptions ia terrestrial gravity, acting on the on the substance of the earth's crust and causing it to be drawn inwards whenever the resistances to such motion are overcome. Mallet and Dana have, indeed, shown that heat was an important factor in those great vulcanian movements which may be regarded as cosmical in importance, those two eailier stages of the earth's vulcanian history during which, first, the crust shrank more quickly than the nucleus and was rent by the resistance of this central mass ; and later, ths nucleus contracted more quickly than the crust, which had to close in upon the central mass in a series of wrinklings or corrugations. But even then the action of gravity was the chief cause of the change wrought. In the present or third stage of the earth's vulcanian history, matters have been altered. The direct action of heat is no longer the cause of subterranean activities, but the indrawing action of gravity, and the grinding of rock masses against each other in those parts of the earth's crust (nearly all of them close by water) where the equilibrium is least secure and the internal resistances are least regular. It is impossible to speak of the destruction wrought at Cassamicciola without referring to the hideous selfishness displayed by those among the inhabitants who made their living by affording accommodation to visitors. It was known for several daye before the earthquake that danger was impending. But hotelkeepers and the like concealed the evidence of danger or made light of it, " for had it been known," these murderously-selfish wretches are good enough to explain," all would have fled, and we should have lost the profits of the season." Through this three or four thousand persona lost their lives, ard many more have been ruined. For cool wickedness the conduct of these Ischian hotelkeepers has scarcely been surpassed in the lecords of the human race.

It is noteworthy that the destruction afc Casamicciola far exceeded that which look place at Pompeii. It was also far more sudden. The destruction of Pompeii was the work of several days. Casamicciola and five or six other small towns were destroyed in about a quarter of a minute. Of about 12,000 inhabitants of Pompeii, some 500 or 600 ' were killed. The total population of Ischia is about 20,000, of whom more than 3000 have been destroyed. As an eye-witivess of the desolation produced in Ischia has said, " Casamicciola no longer exists, and it is doubtful whether it will be ever re-built, for Ischia appears to be re-asserting itself, and to be again assuming the charac'er of a dangerous volcano."

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