162 THE OCEAN RIVER 



But in addition to the force of the wind or of the rapid 

 advance of tidal waters rising up to twenty feet, the force of 

 the accumulated rainfall is tremendous. In Porto Rico in 

 1899 a particularly severe storm deposited more than two and 

 a half billion tons of water on that island. This force, plus 

 the violent changes in the barometric pressure of the air, may 

 account for the frequent recordings of earth tremors during 

 the progress of a hurricane. It has been calculated by Brooks 

 that a barometric drop of air pressure of two inches removes 

 a load of two million tons from each square mile of the earth's 

 surface. A ten-foot rise in water would add nine million tons 

 of pressure to each square mile. The time and manner of the 

 combination of these forces might be sufhcient to release 

 already existing tensions on the earth's crust. These micro- 

 seisms have been recorded by the Navy Department of the 

 United States at Guantanamo Bay, Cuba, and indicate that 

 the approach of severe storms can sometimes be detected by 

 the increase of earth tremors when the storm center is still a 

 thousand miles away. The elements walk with a giant's tread. 



In our northern hemisphere in the middle latitudes the 

 airs move generally from west to east across the Atlantic to 

 Europe north of the thirtieth parallel. The air currents and 

 the currents of the Ocean River are companion systems that 

 control and influence each other. Between them for ages past 

 they have determined the English and European climate. In 

 conjunction with other forces, the climate of sea and air 

 formed the great age of glaciation that ushered in the time 

 of modern historic man; and they could again bring on an age 

 of ice. 



Now that we have looked briefly at the nature of the climate 

 engine we can drop back in time and see what it has done to 

 foster or hinder the development of our present-day life on 

 earth. 



There has been a distinct evolution of climate as we know 

 it today since the last icecap at about 30,000 b.c. — the time 



