170 THE ALUMNI JOURNAL 



— either the earth is getting hotter or radio-active processes are differ- 

 ent under these conditions from what they are in the laboratory. Up 

 to the present no one has been able to affect in any way the velocity of 

 radio-active transformation, either by the action of high pressure or 

 by high temperatures. 



It seems possible that the outer part of the earth's crust is very 

 different from the interior and this condition may be due to the accu- 

 mulation of comets, shooting stars and other cosmical matter over 

 the earth's surface. There may be an outer criistal zone containing 

 radio-active matter to a depth of 30 miles and possessing li- density of 

 about 2.8. Extending below this for some 600 or 800 miles there is 

 a stony zone of a density of 3.4, while the remainder of the earth is 

 possibly largely composed of iron, with a density of about 8. These 

 zones can be explained on the planetesimal theory without assuming 

 that the earth has been in a molten state. The transmission of earth- 

 quake waves and tremors also requires the existence of zones. 



The accumulation of helium in the rocks and the radium, uranium 

 and lead ratios probably serve as the best reg"istering thermometers 

 of time that geologists possess. The work of Strutt and others in 

 determining these ratios indicate that the earth is really an "old world''' 

 after all, much older than we used to think. The ages of the various 

 rocks are about as follows : 



Carboniferous rocks 340,000,000 years. 



Devonian rocks 370,000,000 years. 



Ordovician rocks 430,000.000 years. 



Algonkian rocks 1,000,000,000 years. 



i\rchaean rocks i ,300,000,000 to 1,600,000,000 years. 



Continued work of this kind will undoubtedly serve as a very 

 important aid in really making geology a chronological science and 

 giving "dates" to geological history. 



•The Possible Radio-activity of the Sun and Stars.- — The 

 presence of considerable amounts of helium (helium gas was first 

 discovered in the sun and is named for it) in the solar atmosphere 

 would lead one to suppose that this helium came from the disintegra- 

 tion of uranium, thorium or other radio-active substances in the sun. 

 The properties of the aurora indicate that these may be due to alpha 

 and beta like radiations from the sun striking our atmosphere. This 

 with some evidence of radium and radium emanation in the solar 



