THE EARTH'S INTERIOR.

Rangitikei Advocate and Manawatu Argus, Volume XXXIV, Issue 9165, 8 June 1908, Page 6

THE EARTH'S INTERIOR.

A 6000 MILE CORE OF IRON. Professor Wiechert, a German savant, has arrived at the conclusion that the centre of the earth consists ox a core of iron nearly 6000 miles in diameter, surrounded by a stony shell about 1000 miles thick, on the surface of which we dwell. His reasoning is based on a study of earthquake shocks and tremors. Everybody must be aware by this time, says Professor Serviss, of one of the most startling and wonderful of . a H the discoveries of modern science—namely, that a heavy earthquake shock is not felt plainly in the crust of the earth, but that it sends waves straight through the globe in all directions. Seismological observations in widely separated countries frequently record these waves or tremors, and the observers, by a comparison of observations, are able to say “There has been an earthquake. ’ ’

Not seldom it happens that a shock occurring in the middle of an ocean, far from any land, is thus recorded and, since no damage is done, its occurrence would never have been known but for the tell-tale tremors sent through the globe. At first it was all that the seismologists could do to establish tha simple fact of the existence of these world-wide tremors afiecting the entire frame of the great planet. But now the instruments used h»ve become so delicate, and they have been established at so many points on the earth, that the peculiarities of different sets of earth-waves can be detected, and their varying velocities measured. It is upon this fact that Professor Wiechert founds his conclusions. To indicate the nature of his work it is enough to say that' he finds that the average velocity of the preliminary tremors of an earthquake is about four and a half miles per second at the surface of the earth, but that It gradually increases up to a depth of 800 or .1000 miles, and then it suddenly leaps to nearly eight miles a second. The gradual increase of the velocity of the waves is to he. ascribed to the increase in the density of the earth’s crust, owing to the presence of the superincumbent layers. But the sudden increase of velocity at a depth of some 1000 miles shows that a great change in the character of the substance of the earth must occur there. It must become suddenly far more dense and aolid'than it is above and the velocity with which the tremors traverse this part of the interior of the globe indicate that the material concerned is iron. Hence the conclusion that the core of the earth consists of iron, in a vast globular mass, nearly 6000 miles in diameter. It is no matter of surprise to scientists, Professor Serviss adds, to finds that the earth has an iron core, because its magnetism has alwavs been an indication of that faot, but the manner in which the fact is established is highly interesting.

At a depth of some twenty miles, according to Professor Wiaechert, there must bo a layer of liquid, or plastic material, the presence of which is shown .by certain long ribrations which have an average period of eighteen seconds. But the greater part of the interior of the earth is not composed of matter approaching the liquid state. The heat may be great enough to melt any known material, but the pressure is so immense that it is held in a virtually solid state.