286 The National Geographic Magazine 



years. This average has been main- 

 tained since 1870 ; but no storm has 

 left such an appalling record as the one 

 of September 8, 1900, known as the 

 Galveston hurricane, and it is not prob- 

 able that we shall again see its counter- 

 part on the Texas coast in centuries. 



It is a meteorological coincidence that 

 the West Indies bear the same storm 

 relation to the United States that the 

 Philippines do to China and Japan. 

 With the new possessions of the United 

 States in the Orient it has been possible 

 to establish a storm- warning service that 

 is as valuable to the commerce plying 

 the waters contiguous to the China coast 

 as the service recently organized in the 

 West Indies is to our southern seas. 



The hurricanes that occur in the Phil- 

 ippine Islands are called typhoons. Like 

 the West Indian storms, they occur 

 mainly during four months of the year — 

 the middle summer and early fall. The 

 late Father Vines, S. J., a scientist who 

 gave much study to tropical storms, says 

 it must be admitted that cyclones do not 

 form at any place within the tropical 

 zones, but that they single out for their 

 formation definite regions within those 

 zones. These regions are always on the 

 southwest periphery of some of the great 

 permanent ocean anti- cyclones. The 

 conditions for the development of cy- 

 clones in the tropics are best satisfied 

 when large continents lie to the west, 

 whose coasts trend northward and south- 

 ward, with extensive seas to the east. 

 Such, at any rate, are the geographic 

 features that concur to form the cyclone 

 regions of the West Indies, of the Phil- 

 ippine Islands, of the China Sea, of the 

 seas of India, of the region east of Africa 

 in the vicinity of the islands of Mada- 

 gascar, Mauritius, Reunion, Rodriguez, 

 etc. 



The cause of all tropical hurricanes 

 may be made clear by confining the ex- 

 planation to a description of the condi- 

 tions that permit of the formation of the 

 West Indian storms, which are as fol- 

 lows : 



Normally there is a belt of heavy air, 

 of about 10 degrees of latitude in width, 

 lying just north of the tropics, which 

 interposes an almost impassable barrier 

 to the movement of cyclones north- 

 ward. The region of greatest pressure 

 of this belt is about the middle of the 

 Atlantic Ocean. By August the heat 

 of summer acting on the North Amer- 

 ican continent has raised the tempera- 

 ture of the air over the land much more 

 than it has that over the water, and the 

 land portion of the high-pressure belt 

 is dispersed, leaving an opening for the 

 escape northward of tropical storms, 

 which form in the ocean on the south- 

 west periphery of the great high- press- 

 ure that so persistently remains central 

 over the ocean. From this place of 

 origin the hurricanes are carried north- 

 westward by the general circulation 

 of air outward from and around the 

 big high. This grand summer circu- 

 lation of the air of the Atlantic Ocean 

 brings the tropical storms nearly or 

 quite to our South Atlantic or Gulf 

 states before they recurve to the north 

 east in pursuing their course around the 

 high. This anti-cyclone of the ocean 

 differs from those that have heretofore 

 been described, in the fact that it quite 

 doggedly holds to nearly the same geo- 

 graphic position. It covers the whole 

 southern ocean, and as the currents of 

 air spirally flow outward, in a direction 

 that agrees with the circulation of the 

 hands of a watch, they frequently break 

 up into small cyclonic whirls of 100 to 

 300 miles in diameter on the outer rim 

 of the large anti-cyclone, and especially 

 along the southwest quarter of the rim. 

 The air as it runs down through the 

 anti-cyclone feeds the vortices that form 

 at the outer boundaries of the high. 

 The vortex may whirl with the violence 

 of a hurricane, and it usually does ; but 

 in its course westward and then east- 

 ward it clings to the outer hems of its 

 parent — the anti- cyclone. 



The wonderful sweep of the West 

 Indian cyclone is made clear by the 



