ABOUT EARTHQUAKES.

New Zealand Herald, Volume XLVIII, Issue 14751, 5 August 1911, Page 5

ABOUT EARTHQUAKES.

SCIENCE FOR THE PEOPLE The mystery of. earthquakes ~<> was >" dealt with last evening' by, Mr. G. Hogbenj in 'a lecture at the Leys Institute. ;;;Mr. Hogben is inspector-general of schools, and was previously a busy schoolmaster; but during the past * quarter of a century he has been able to, make an elaborate study of earthquakes and their ways, 1 and to make certain discoveries from his' studies. To make his lecture intelligible, Mr. Hogben had first to side-step into geology and explain what folds and faults in rock-beds are, and to speculate upon "thickness of the earth's crust arid the probable state of the body of the earth, as to its plasticity or, otherwise. This led at once to the explanation of the formation of folds by the shrinking of the under , layers of the crust. The upper layers have to fall by their own weight as their supports shrink away; and being too big to-fit in their new r position they: have to crumple up. The lecturer then explained • how vast quantities of material washed down by rivers lighten the land 1 masses and load the sea-bed till . iha latter sinks and the land rises correspondingly. • ■ ■ A discussion of such a subject in a cold scientific light, and :, contemplation of the Idea that contributing causes go on continually, may have bred some discomfort in the audience, and a welcome reassurance : was ' felt when Mr. Hogben recalled a little joke upon this city's almost complete ; immunity from earthquakes "it's another injustice to Auckland." Such tremors as have occurred here have usually been so small as to be unobserved by the ; people, "'though, of course," Mr. Hogben remarked. '"■'- Wellington man would have been, able to -feel,them." ■Dealing with some of the great earthquakes of recent years, Mr. Hogben explained that the famous Mount Pelee eruption was probably the result of a series of big. shakes, which weakened the crust and iallowed : bottled-up forces to break out. The San Francisco earthquake naturally provided matter for much of the address, and a large number of slides showing the damage done to the buildings and the evidences left in the ground of the nature of the responsible earth-shift were shown. Among the slides shown were photographs of the seismograph records of this and other earthquakes, made at the Wellington and Christchurch observatories. , The audience, which-: filled the lecture hall, and which was presided over by Mr. T. W. Leys, found the lecture of great interest, and ' learned many probably unsuspected points of valuable knowledge. '