302 ANNUAL OF SCIENTIFIC DISCOVERY. 



to upper or returning " trades ; " if this be true, the north-east and 

 south-east " trades " ought to be the minimum of ozone currents, 

 the one in the northern hemisphere forming the south-west wind, 

 and the other in the southern hemisphere a north-west wind. 



TRANSPORTING POWER OF THE FOG-VESICLE. 



That fogs and mists possess the power of transporting vapors, 

 gases, odors, and the like, or even minute solid particles, as in 

 smoke, is a fact well known to the observant. Many persons 

 dwellino* far to the leeward of certain manufacturing establish- 



^D ^j 



ments are well aware that offensive or irritating gases may be 

 caught upon the lap of a fog, as they issue from the chimneys of 

 the factory, and carried away for miles. The same thing is appar- 

 ent when the sea-fog sweeps inland, bearing the " smell of the 

 sea, 11 as the landsman calls it, or when the land-mists drift out on 

 to the ocean, carrying to the incoming mariner the " smell of the 

 land," the odors in question, both that " of the land" and that 

 "of the sea," being, in reality, one and the same, namely, the 

 odor of the strand. 



A somewhat analogous instance of the transporting power of 

 the mist is seen in the long-persisting and all-pervading smoke- 

 fogs which arise from burning forests and peat-bogs toward the 

 close of our northern summers. These autumnal smokes are 

 really of the nature of mists, as will appear from a moment's re- 

 flection upon the manner of their formation, and upon the chemi- 

 cal composition of the products of the combustion of a forest. A 

 very large proportion of these products is nothing but aqueous 

 vapor, which, under the peculiar circumstances of the case, im- 

 mediately assumes the vesicular condition which we see in fogs 

 and clouds. 



In defiance, then, of all the ordinary laws which control the dif- 

 fusion of gases, fogs can buoy up, hold for a long time, and carry 

 to great distances, odors and vapors which, under ordinary con- 

 ditions, are but slightly volatile ; and in the same way, though in 

 a lesser degree, they can transport solid substances. Beside the 

 soot above mentioned, another familiar instance of this transport- 

 ing power, as regards solids, is that of the boracic acid brought up 

 by steam jets which issue from the earth in the volcanic districts of 

 Tuscany ; and there is another striking example of the same thing 

 in the salt which is carried inland by fogs from the ocean. As an 

 evidence of the extent to which this process goes on in some 

 localities, we may cite the experience of the farmers upon our 

 eastern seaboard, where fogs are frequent. It is there found, even 

 at distances of 10 or 15 miles from the salt water, that ani- 

 mals have none of that craving for salt which is so strong in the 

 cattle of the inland districts; and the farmer consequently pays 

 no heed to a matter which is so important elsewhere. He takes 

 no pains to " salt his cattle," for he knows from long experience 

 that they will obtain a sufficient quantity in and upon the grass 

 which they daily eat. 



As bearing upon these well-known facts, the system of apply- 



