CONTEIBUTIONS TO METEOROLOGY. 



45 



Table XXVIII. — IStorms advancing westerly over Eurojte and the Atlantic Ocean. 



and 41 are of this class. It will be noticed that in three cases the same number occurs in three of 

 the preceding lists, antl in twenty cases the same number occurs in two of these lists. 



61. It may be objected that if I assign two or three causes for the same phenomenon the 

 I)robability is that I have failed to discover the true cause. To this objection it may be answered, 

 that the three causes here assigned are all intimately related to each other, and maj- all concur in 

 the same phenomenon, or in different stages of the same pheuomenou. It will be shown hereafter 

 that the surface winds blow outward Irom au area of high pressure, and circulate around the 

 center from left to right, as shown in the outer portions of Plate XIV, Fig. 2. Now sui)pose that 

 two areas of high pressure are situated at a distance from each other not much greater than the 

 sum of their radii, and that the air between them is quiet, and the i)ressure does not ditfer much 

 from 760'"™ or .30 inches. These two areas of high i)ressure exert au influence to set the air between 

 them in motion, in such a manner as to circulate from right to left about a center. The inward 

 motion which attends this circulation cannot exist unless a portion of the air within this area 

 ascends above the earth's surface. This air, in ascending, becomes cooled, a portion of its vapor is 



