THE BIRTH, LIFE, AND DEATH OF A STORM. 685 



storm of wind at all. In partial confh-mation of this view, Professor 

 Mohn, of Christiania, points to the accidental condensation of moisture 

 caused by the contact of a mass of damp air with the surface of an ex- 

 tensive snow-field as a possible cause of a storm. About the sixty-first 

 parallel of latitude the glacier region of Justedal stretches for several 

 miles along the coast of Norway, and this has occasionally been known 

 to exert an influence in increasing the intensity of an existing cyclone, 

 and even in some instances has appeared as the center of a newly- 

 formed depression. 



These gentlemen, moreover, rely greatly on the fact that the rain 

 area which accompanies every cyclonic system is roughly oval in shape, 

 with its longer axis extending in the direction in which the system is 

 advancing, and that by far the greatest amount of rain falls in front 

 of the storm. They do not, however, explain the fact that very heavy 

 rain frequently occurs on the northern side of a depression, where the 

 wind is easterly, and that this circumstance does not indicate a north- 

 ward motion of the system. 



The most serious objection to this theory is, however, that first 

 stated, that not only do the heaviest rains not come with the severest 

 storms, but that frequently they are observed in times of nearly abso- 

 lute calm. 



2. The second theory to which I shall refer is the mechanical one, 

 most strongly urged by Mr. Meldrum, of the Mauritius, whose investi- 

 gations into the weather over the Indian Ocean have led him to the be- 

 lief that every cyclone is generated in the intervening space between 

 two oppositely flowing currents of air, of which the easterly moving 

 stream, speaking in the most general terms, lies on the polar side of 

 the westerly wind. Such a disposition of the currents would be that 

 which would naturally arise were the cyclone once formed. 



This view is called seriously in question by Messrs. Blanford and 

 Eliot in their discussion of recent cyclones in the Bay of Bengal, which 

 they have been able to study from very early stages, and in which they 

 fail to see evidence of the preexistence'of two, and only two, determi- 

 nate currents. 



Another serious objection to this theory is that it does not assign a 

 vera causa sufficient to give the first impetus to the barometrical fall 

 and the rotatory movement of the air. 



3. A third theory of the origin of these storms is that which is 

 strongly urged by M. Faye, in Paris, and is to the effect that, as inter- 

 fering currents in rivers give rise to vortices which extend from the 

 surface downward into the water, so all our water-spouts, trombes, and 

 even the largest tropical hurricanes must be all formed in the upper 

 regions of the atmosphere, and extend downward to the earth : the 

 force which gives them their onward motion being supplied by the 

 upper currents. 



It is sufficient to say that this theory has not met with acceptance 



