Arizona silver belt., 1900-02-08
THEINSIDE OF THE EARTH
There is no Molden Sea, but a Core
 Twice as Rigid as Steel.

Twice as Rigid as Steel.
 In the February number of Me Clue $ Magazine, Mir. Cleveland Moi fett reports an interesting interview with Professor Milne, under the title, "The Inside of the earth" in which are given the now famous earthquake observers conclusions as to the inter- for of our planet The interior of the earth, although it has been cooling 10000, 900 years, according to Lord Kelvin, and l00, ,000,0 ,000, according to the geologists, is still pretty hot. There is a rough and ready rule that the temperature rises l degree Fahr- enheit for every 5l feet you go down. Professor Milne shows that this rule is nonsensical by suppoSing a depth of 1000 miles, which, according to this rule would give temperature of 100,- 900 degrees, an absurd conclusion, and he explains that after certain point, say POO miles below the surface, the rate of increase is hardly appreciable.
 The most interesting feature of Pro lessor Milne $ theories came in answer to Mr, Motfett'S question concerning ''the great molden sea that we might expect beyond this POO miles, The professor says there is no molten sea at all, but on the contrary great rigid core, and that the mass of ores and chemicals existing at this enor- nous heat is at least twice as rigid as steel. This theory is based on the ob- servation of seismic waves. The ra pidity of the travelling of these waves varies directly with the rigidity of the medium. The professor finds that seismic waves starting in Japan and coming necessarily through the center of the earth reach the Isle of Wight in sixteen minutes, nearly twice as fast as they would come the same dis tance through solid steel. Hence the conclusion that the matter inside the earth, although at this tremendously high temperature, is as rigid again as steel.
 "These phenomena, invariably noted at all our seismic observations, en- tirely upset the old theory that the earth's interior is freely moving liq- uid, and demonstrate apparently that the earth orange, under its peel of crust is mass very much more rigid than the crust itself"
 Yet extremely hot?"
 ''Of course.'
 'So hot that everything would melt if it could. And everything does melt in a certain limited region, sort of viscous layer, pasty in its upper parts and solid down below"
 'Why not molten all the way down."
 Because of the pressure above. At a depth of POO miles this would amount to about 600 tons to the square inch, probably enough to squeeze the molten rock and metal back into solid state. At any rate, depth must soon be reached where the pressure is great enough to effect that result. You know the general law-that heat ex- bands and cold contracts. Well, there are strong reasons for believing that | most metals and rocks can be pre- vented from melting under heat if you can prevent them from expanding. | Or, if you have quantity of molten metal which has already expanded in melting, you can bring it back to the solid state by great pressure, just as you can solidify liquid aid by putting It under great pressure. The interior of the earth--the ball of the orange underneath the peterborough poten- ually liquid, is actually solid and ex- tremely dense. Itwould immediately become liquid if the pressure were re- moved. It is hot enough to become liquid, but by the laws of matter can not do so without expanding, and it cannot expand so long as it is squeezed down under the great weight upon it. You must understand that the earth, liquid, became solid under two influences: 1t began to solidify at the surface by cooling, the crust grow ing thicker and thicker; and it began to solidify at the center by pressure, the core growing larger and larger. This double phenomena of soldifying continued until solid outer shell and a solid inner core came close together in what may be called the critical region of the earth, region that feeds | lava to volcanoes"
 Work on the Tres Amigos gold mine in the Orc Blanco district owned by