THE CAUSE OF EARTHQUAKES.

Ashburton Guardian, Volume XXIX, Issue 7733, 1 March 1909, Page 4

THE CAUSE OF EARTHQUAKES.

Professor Milne, F.H.S., who lias charge of the seismographs at Shide, in the Isle of AVight, gives this'description of the cause of the earthquake in Sicily and Italy. Writing to the London Daily Mail, he says: "I have personal knowledge of the district in which the great earthquake has occurred, but were I to revisit it 1 should wonder whether my former visit had been a reality or was simply a dream I What do these- great convulsions mean? What is their cause, and what are their effects from an historical point, <j£ view ? We look to Italy as a teacher of the past; but, from the point of view of the earth's history, Italy is one of the youngest of European countries, or, to be a little more definite, Jot me my that about the time when the' materials were being deposited which ;\jrmed the noble downs of Southern England, Italy was represented by a .-itring of islands. Since that time the subterranean ridge, the outcrop of which the islands represented, has been growing upward until the string of islands was joined to form the peninsula of Italy. This upward growth has not yet ceased; the process is still going on', and the face or the world in this part cf Europe may be Ukenpr] fp that cf an old man. As we 'grow ■older, ■ muscular and adipose tissue gradually disappear, and the skin is ici't too hirgo 10 cover the original surface; therefore, it wrinkles. The action in Italy is still in progress. We have, for example, the often-quoted case of the Temple of Jupiter Serapis, early in 1800, which was sinking at the rate of about an inch every four years. Sin.cc the lloman period, when the temple'was' imiii, the ground has ■sunk more than 20 feetf' below the ley..* of the ocean, A similar activity 'provails iijong the coast of Italy, and we have many otjipr Illustration's of .earth movement. But as the '^uiisj: of our world is being in places crumbed upward, it is natural to suppose that corresponding depressions must be formed. The action is Hiiit of n co:icertina. When it is heiii" dosed, a ridge goes up nnJ a parallel depression goes down. All this mcnns tli:i't strain is being prodiKvrl, mid wlion limits iip.* reached fraotir.-es take place, i'd'owvil by sudden dislocations. Thenc disfcrations . may be many miles in lon^lli. The iiinin dislocation in the San Francisco eavthquakt; ,-.i".jnv; t.O have had a length exceeding 400 miles;. Aii.u.'c such a line huge masses of niateri;;! fall downward;) with it series of inicrinittent jolts, l^r-uiit ujifjt I can see by my seismograms at Shide, ihoi'i' were at least fifteen of those in connection with the earthquake in Italy. The blows which thoso represented evidently reached - the homogeneous material which constitutes the interior of the worfd, and which, on account of its rigidity,".announced the Italian disaster to every spot; on earth provided with suitable instruments for recording it-"