THE ENGINE OF THE AIR 157 



forecasting. Any permanent change in the domination of the 

 polar front by the warmer low-pressure cyclonic storms from 

 the south would most certainly be reflected in the delivery of 

 warmer waters to the north by the Ocean River, and the com- 

 bination of wind and water would affect the Arctic icecap. 

 Some such drastic change is believed to have had a great deal 

 to do with the recession of the great icecaps that overlay 

 North America and Europe thirty thousand years ago. But 

 before we take a look at early climatic changes and the days 

 of the retreating ice, we should first briefly study the nature 

 of a cyclonic storm as an engine of climate. 



The king of cyclonic storms in the North Atlantic Ocean 

 is, of course, the hurricane. William Dampier more than two 

 centuries ago gave a good description of the approach of such 

 a tempest. 'The clouds," he said, ''which precede a hurri- 

 cane, are different from the North Banks of a norther which 

 are uniform from horizon to horizon. The hurricane clouds 

 tower up their heads pressing forwards and are yet so linked 

 together that they all move alike. The edges of these clouds 

 are gilded with various and afrighting colors, the very edge of 

 all seems to have a pale fire-color, next that of a dull yellow 

 and nearer the body of the cloud is copper color but the 

 body of the cloud itself, which is very thick, appears extraor- 

 dinarily black." William Gerard de Brahm, one of the first 

 Americans interested in the study of weather and the Gulf 

 Stream, quoted this story of the great Florida storm in 1759: 

 "A heavy gale from the northeast so impeded the current 

 of the Gulf Stream that the water forced, at the same time 

 in the Gulf of Mexico by the trade winds, rose to such a 

 height that not only the Tortugas and other islands disap- 

 peared, but the highest trees were covered on the Penninsula 

 of Largo, and at this time the Litbury, John Lorain master, 

 being caught in the gale, came to an anchor, as the master 

 supposed, in Hawke Channel, but to his great surprise found 



