NKW THEOKY OKTHK <>Kl(4lN OF THE EARTH. 39 



hilling inalerial of world growth. .-Sulj-sequeiitly the |)ressure and 

 i-ising temperature forced it further southward.'' 



I referred, a few minutes ago, to the moon, remarking that it 

 was not till the earth had grown larger than our hilver-clieeked 

 satellite that it began to manul'acture an atmosphere for itself. 

 The moon is supposed to have no atmosphere, to be frozen and 

 dead. According to the new theory of i)lanetary formation, this 

 is because its growth was arrested, in consequence of the scar- 

 city of material, l)efore it grew so large as to have gravitational 

 power enough to retain the gases ot which air and water are 

 composed. Its development was arrested by lack of nutriment. 

 Tt was [)lanted too near the earth, which got a good start of it, 

 and the eartii 'drew to herself most of the planetary material in 

 the region of their influence. And so the moon stopped growing 

 before she could stand alone, so to speak. She is. not a dead 

 planet, but a planet in an arrested i^tage of development. The 

 sun, at the other extreme, may be merely an overgrown globe. — 

 the spectroscope showing that it is composed of the same 

 elements as the earth, — whose mass is so tremendous that pres- 

 sure keeps its surface in so continuous a state of volcanic erup- 

 tion that it is envelopetl by a fiery atmosphere of gases thrown 

 out from its interior. The si)ots on the sun may be the mouths 

 of inactive volcanoes, seen through the gaseous envelope that 

 surrounds that luminary. 



This new theory of world origin also involves a new idea of 

 climate from the earth's beginning till now. '"Instead of the 

 highly carbonated atmosphere of early geologic ages," says Prof. 

 Fairchild, "according to the old theory, with slow decarbonating 

 and cooling, culminating in the cold climates of the 

 present time and pointing to a final winter, we can regard the 

 past climatic conditions as not greatly unlike those of the pres- 

 ent. We shall recognize that throughout geologic time there 

 have been such variations in climate periods of cold and aridity 

 or of heat and moisture as we know have occurred since the 

 Middle Tertiary (about the time that mammals appeared on the 

 earth)." 



Just what has made these variations in climate is accounted 



