EARTH-LIFEFORMATION. 377 



Looking at the Earth's appearance around 

 us, we see it divided into three physical ele- 

 ments air, water, land a gas, a liquid and 

 a solid. These we set down in the probable 

 order of their origin. In the great transition 

 of the Earth from its original mass of lumin- 

 ous nebula or fire-mist, the air or atmosphere 

 was doubtless the first to evolve; out of this 

 air must have come as it cooled off the liquid, 

 water, which is composed of the gases oxy- 

 gen and hydrogen. Still further, of this water 

 sprang land which still often shows, even on 

 the mountain tops, so many signs that it once 

 had its home in the bottom of the sea. In 

 such way science at present conceives the 

 Earth's Organism to have been differentiated 

 into its three main elements in the lapse of 

 geologic ages. 



The first fact about the terrestrial air is 

 its continual motion. As it is gaseous, its 

 particjes or molecules are expansible, self- 

 repellent, though still subject to gravitation. 

 The next fact about the Earth's atmosphere 

 is that it moves in currents, and that these 

 currents, after detours long and short, come 

 back to their starting point. For instance, 

 there is the universal sweep of the winds to- 

 wards the equator and then their deflection 

 and return toward the poles, mainly caused 

 through the sun's heat. But in this general 



