THE ATMOSPHERE AND ITS CURRENTS. 459 



sional disaster. A variety of natural causes in operation upon the surface of the globe, 

 and in its interior, concur to derange that constitution of the atmosphere which is alone 

 salubrious, to vitiate the fluid, convert the medium of life and health into a cause of 

 fever, pestilence, and death, thus changing every scene where the machinery of human 

 existence is in movement into a Grotto del Cane, completely arresting all its wheels an 

 effect which would undoubtedly transpire without an antagonistic influence in constant 

 action. In the process of supporting mankind and animals, the atmosphere is deprived 

 of its oxygen, and exhaled in a morbid condition unfit for combustion and the sustenance 

 of life ; and the respiration of plants contributes also to its derangement. The exhala- 

 tions from the low swampy regions of the earth are a further cause of deterioration, and 

 hence the malarious mass to which the Pontine marshes, and similar districts, give birth. 

 The provision against the reduction of the atmosphere to a universally disorganised and 

 vitiated condition is the currents that prevail in it, which disperse and separate the 

 poisonous ingredients, render them innocuous by bringing them into new combinations, 

 and thus keep up that due proportion between the component parts of the aerial envelope, 

 upon which its life-conserving property hinges, yet which the functions of life are per- 

 petually destroying. The ordinary play of the winds, whispering in gentle breezes and 

 rushing in powerful gales, has been ordained by the Author of life to subserve this pur- 

 pose, and the dread tornado is also an efficient agent in the regeneration. In its alembic, 

 it has been remarked, " the isolated poisons will be redistilled ; by the electric fires 

 which it generates, their deleterious sublimations will be deflagrated ; and thus will the 

 great Alchymist neutralise the azotic elements which he has let loose, and shake the 

 medicinal draught into salubrity." The baneful effects of a stagnant condition of the 

 atmosphere are exemplified in the feeble physical frame, and short term of years, of those 

 who in the " city full " are cooped up in sites were there is no sufficient ventilation, and 

 the inhabitants of many deep enclosed valleys exhibit physical and mental deterioration as 

 a consequence of the same cause. The numerous examples of cretinism, or idiocy, with 

 goitres, found about the villages and hamlets of the Lower Valais, and the Val d'Aosta 

 in Switzerland, valleys, which have low marshy spots at the bottom, surrounded by high 

 mountains, where the fresh air does not circulate freely, and where the reflected rays of 

 the sun are very powerful in summer, Saussure attributed to the stagnation of the 

 atmosphere ; and though such instances of physical deformity and intellectual incapacity 

 may be the combined effect of various causes, it is in harmony with the known effect of 

 the one referred to, to suppose it materially to contribute to the result. The cagots of 

 the deep Pyrenean valleys answer to the cretins of the Alps. 



In closing this notice of atmospheric currents, we refer to observations made upon the 

 ordinary winds of Great Britain. From an average of ten years of the register kept by 

 order of the Royal Society, it appears that at London the wind blows annually in the 

 following proportions: 



Days. Days. 



South-west - - -112 



North-east - - 58 



North-west - 50 



West - - 53 



South-east * - -32 



East - - 26 



South - 18 



North - - - 16 



The same register shows, that the south-west wind blows at an average more frequently 

 than any other wind during every month of the year, and that it blows longest in July 

 and August ; that the north-east blows most constantly during January, March, April, 

 May, and June, and most seldom during February, July, September, and December ; and 

 that the north-west wind blows oftener from November to March, and more seldom during 

 September and October, than any other months. At Bristol, the south-west winds are 



