THE LAW OF STORMS DEVELOPED. 397 



velocity and violence to the air-current. It is, therefore, in the air- 

 current that the homeward -hound vessel from the Cape of Good Hope 

 aims to steer, hecause she is sure of being wafted happily and swiftly 

 to her destination. 



It has long ago been demonstrated by meteorologic observations, 

 taken both at sea and on land, that there is very much less atmosphere 

 in the Southern Hemisphere than in the northern, and for a long time 

 physicists were at a loss to account for the difference. It has been, 

 however, very satisfactorily explained by the eminent American 

 mathematician, Ferrel, in his work on the "Motions of Fluids and 

 Solids, relative to the Earth's Surface," where he proves at length, 

 and states in detail (p. 39): "As there is much more land, with 

 higher mountain-ranges, in the Northern Hemisphere than in the south- 

 ern, the resistances are greater, and consequently the eastward motion 

 of the air, upon which the deflecting force depends, is much less ; and 

 the consequence is, that the more rapid motions of the Southern Hemi- 

 sphere cause a greater depression there, and a greater part of the at- 

 mosphere to be thrown into the Northern Hemisphere" It is, doubtless, 

 to this tendency of the Southern Hemisphere to throw off much of its 

 atmosphere north of the equator that we may attribute in part the 

 superior force and power of the southeast trades, and their well-known 

 ability to battle with the northeast trades, and drive them from their 

 own territory, at least all summer, and even in winter, as far back 

 across the line as 3 or 4 north latitude. Mr. Ferrel, speaking of the 

 principle just enunciated, well says: "This also accounts for the mean 

 position of the equatorial calm-belt being, in general, a little north of 

 the equator. But, in the Pacific Ocean, where there is nearly as much 

 water north of the equator as south (and the resistances are usually 

 equal), its position nearly coincides with the equator." In other words, 

 just as a bucket full of water set to revolving on a perpendicular axis 

 would show a depression in the centre, and the fluid be thrown from 

 all sides of its rim, the Southern Hemisphere throws its water and its 

 atmosphere into the Northern Hemisphere, all along the equator. 



It is, therefore, a mathematical and mechanical certainty that there 

 is an invasion of the northeast trade-wind belt from the southeast 

 trades, and observation powerfully bears out the deduction of the 

 mathematician. Auste states, in his cautiously-written " Physical 

 Geography : " " The southern trade-wind region is much larger than 

 the northern in the Atlantic Ocean. In this sea, the southeast trades 

 are fresher, and blow stronger, than the others, and often reach to 

 the 10th or 15th parallel of north latitude; whereas, the northern 

 trade-wind seldom gets south of the equator, and usually ranges from 

 9 to 29 north latitude " (p. 253). It is easy to see how easily it 

 happens that a very small atmospheric eddy found in the tropical 

 Atlantic by the conflictoiy northeast and overleaping southeast trade- 

 winds may soon become a hurricane of wide extent and of tremendous 



