136 A HISTORY OF 



r ormer chapter, almost every substance contains some portions of aj; 

 Vegetables, or the bodies of animals left to putrefy, produce it in a 

 very copious manner. But it is not only seen thus escaping from 

 bodies, but it may be very easily made to enter into them. A quan- 

 tity of air may be compressed into water, so as to be intimately blend- 

 ed with it. It finds a much easier admission into wine, or any fer- 

 mented liquor ; and an easier still, into spirits of wine. Some salts 

 suck up the air in such quantities, that they are made sensibly heavier 

 thereby, and often are melted by its moisture. In this manner, most 

 bodies, being found either capable of receiving or affording it, we are 

 not to be surprised at those streams of air that are continually fleeting 

 round the globe. Minerals, vegetables, and animals, contribute to in- 

 crease the current ; and are sending off their constant supplies. 

 These, as they are differently affected by cold or heat, by mixture or 

 putrefaction, all yield different quantities of air at different times ; 

 and the loudest tempests, and most rapid whirlwinds, are formed from 

 their united contributions. 



The sun is the principal instrument in rarefying the juices of plants, 

 so as to give an escape to their imprisoned air ; it is also equally ope- 

 rative in promoting the putrefaction of animals. Mineral exhalations 

 are more frequently raised by subterranean heat. The moon, the 

 other planets, the seasons, are all combined in producing these effects 

 in a smaller degree. Mountains give a direction to the courses of the 

 air. Fires carry a current of air along their body. Night and day 

 alternately chill and warm the earth, and produce an alternate current 

 of its vapours. These, and many other causes, may be assigned for 

 the variety, and the activity of the winds, their continual change, and 

 uncertain duration. 



With us on land, as the wind proceeds from so many causes, and 

 meets such a variety of obstacles, there can be but little hopes of ever 

 bringing its motions to conform to theory ; or of foretelling how it 

 may blow a minute to come. The great Bacon, indeed, was of opinion, 

 that by a close and regular history of the winds, continued for a number 

 of ages together, and the particulars of each observation reduced to 

 general maxims, we might at last come to understand the variations 

 of this capricious element ; and that we could foretell the certainty of 

 a wind, with as much ease as we now foretell the return of an eclipse. 

 Indeed, his own beginnings in this arduous undertaking seem to speak 

 the possibility of its success ; but, unhappily for mankind, this inves- 

 tigation is the work of ages, and we want a Bacon to direct the 

 process. 



To be able, therefore, with any plausibility, to account for the va- 

 riations of the wind upon land, is not to be at present expected ; and 

 to understand any thing of their nature, we must have recourse to 

 those places where they are more permanent and steady. This uni- 

 formity and steadiness we are chiefly to expect upon the ocean. 

 There, where there is no variety of substances to furnih the air with 

 various and inconstant supplies, where there are no mountains to di- 

 rect the course of its current, but where all is extensively uniform and 

 even ; in such a place, the wind arising from a simple cause, must have 

 out one simole motion. In fact, we find it so. There are miry p<rt 



