INTRODUCTION 



THE EARTH'S CLOTHING 



It has been calculated that if the earth were tunneled 

 direct to the other side, 7,918 miles would be traveled in 

 making the journey. But a difficulty would be met in 

 this endeavor : After going a few miles, the heat would 

 be so intense that further progress would be impossible. 

 For as we descend into the earth, after going a very little 

 way, the temperature rises at the rate of I degree for 

 every 50 feet, a rate that is universal over the earth's 

 surface, and for the greatest depth attained. 



From the known laws of the conduction of heat the 

 conclusion follows that at a depth of 15 to 20 miles below 

 the surface the earth is red hot, while the heat 100 miles 

 deeper, if applied at the surface, would liquefy all mate- 

 rials at the surface crust. These known facts have led 

 to an hypothesis that the interior of the earth is more or 

 less fluid, and that the crust is only a thin shell floating 

 on the molten globe. 



However, the earth as a body is very rigid and sub- 

 jected to a pressure so great that despite the high tem- 

 perature, the interior is locked into a solid mass as rigid 

 as steel itself. 



But after all, we are concerned less with the interior 

 of the earth and with the surface more. Our aim is to 

 know the outer covering the clothing that encloses this 

 hidden interior and to use its history to our profit and 

 good. Every science has labored with the secret that 

 is hidden in this clothing of the earth that the world 

 might know some of the stories it has to tell : of the 



