HOW THE EARTH WAS FORMED. 



T. C. CHAMBERLIN, 

 Head Professor of Geology, University of Chicag-o. 



JUST how the earth was formed at 

 the outset is not certainly known. 

 The most common view of men 

 of science is that it was once in 

 the form of a fiery gas. It is supposed 

 that all the planets and satellites that 

 now revolve around the sun were once 

 a part of a common mass of gas in the 

 form of a vast sphere which was very 

 large and very hot. This gradually 

 lost its heat and shrank as most bodies 

 do when they cool. If it was not al- 

 ready whirling round at the outset it 

 must have come to do so as it shrank, 

 and as more and more of its heat was 

 lost it rotated more and more rapidly. 

 At length it came to whirl so fast that 

 the outer part, which was moving 

 fastest, could no longer be held down 

 to the surface, and so it separated in 

 the form of a ring around the equator 

 of the great sphere. 



The main mass kept on cooling and 

 shrinking and whirling faster and faster 

 and hence other rings separated. Each 

 of these rings also kept on cooling and 

 shrinking and is supposed to have 

 parted at some point and gradually 

 gathered together into a globe, but still 

 in the form of fiery gas, even though it 

 had lost much of its heat. But at last 

 this globe of gas cooled so much that 

 the main part of it became liquid. 

 This was that part which afterwards 

 became the solid part of the earth. It 

 then had the form of lava. It was still 

 too hot for the water to condense and 

 hence it remained in the form of steam 

 or vapor, forming a vast envelope all 

 about the earth. There are supposed 

 to have been many other vapors in the 

 air at that stage, and it must have been 

 very dense. But at length the globe of 

 lava cooled so that the outer part 

 crusted over, and this crust grew 

 thicker and thicker as time went on. 

 After a while it became cool enough to 

 permit the water to condense on the 

 surface and so the ocean began to be 



formed. The water grew in depth until 

 nearly all the steam was condensed and 

 many of the other vapors that had been 

 in the air while it was so hot were 

 condensed also. And this left the 

 gases which cannot easily be condensed 

 behind, and they formed the air much 

 as it is to-day. And that is the way 

 the atmosphere is commonly supposed 

 to have come about. 



But all this is theory. It cannot now 

 be proved. But there are several great 

 facts that fit in with it and make it 

 seem as though it might be true. As 

 wells and mines are sunk deep in the 

 ground it is found that the earth grows 

 warmer and warmer. Volcanoes pour 

 out»molten rock and this shows that it 

 is very hot somewhere beneath them. 

 Many of the mountains on the earth 

 are really wrinkles in its crust, and it 

 has been thought that these are caused 

 by the cooling and shrinking of the 

 globe. It is because these and other 

 things fit in so well with the theory 

 that most scientific men have come to 

 accept it as probably true. It is known 

 as the Nebular theory. But there are 

 other ways of explaining all these 

 things, and perhaps it may be proven 

 that there are better ways. 



Some scientists have supposed that 

 the earth was formed by small masses 

 or particles of matter gathered in from 

 the heavens. On a clear night shoot- 

 ing stars may be seen quite often. These 

 are little bits of stone or metallic mat- 

 ter shooting through space at high rates 

 of speed, which strike the atmosphere 

 and become hot. The earth also is 

 moving at great speed — nearly nineteen 

 miles per second. It is not strange 

 then that when the little stranger col- 

 lides with the earth it should " make 

 the fire fly." Usually the outside is 

 melted and carried away so fast that 

 the little mass is entirely used up in a 

 few seconds. It merely makes a little 

 streak of light. But sometimes the 



