vi PREFACE TO THE THIRD VOLUME. 



fea, extenfive lakes and rivers, which cover fo large a portion of our 

 globe, muft be highly ufeful, by abforbing what is putrid, for the 

 further purification of our atmofphere ; thus beflowing what would 

 be noxious to man and other aniinals, upon the formation of marine 

 and other aquatic plants, or upon other purpofes yet unknown. 



" Thus we are affured that no vegetable grows in vain, but every 

 «' individual plant is ferviceable to mankind ; if not always diftin- 

 *' guifhable by fome private virtue, yet making a part of the whole, 

 " which cleanfes and purifies our atmofphere. In this the fragrant 

 " rofe and deadly nightfliade co-operate; nor is the herbage, nor 

 " the woods, that flourifh in the moft remote and unpeopled regions, 

 " unprofitable to us, nor we to them ; confidering how ccnftantly 

 " the winds convey to them our vitiated air, for our relief and their 

 ♦' nourifhment; and if ever thefe falutary gales rife to ftorms and 

 " hurricanes, let us ftill trace and revere the ways of a beneficent 

 " Being, who not fortuitoufly, but with defign ; not in wrath, but 

 " in mercy, thus Jloakes the naaters and the air together^ to bury ia 

 «' the deep thofe putrid and peftilential effluvia, which the vegetables 

 " upon the face of the eartli had been infufficient to confume [c]." 



We may add to the lift of reftoratives, the aromatic odour of plants 

 and the irrigation of fliowers, whofe refrefhing efifeds on the at- 

 mofphere are fo immediate and forcible, as toftrike our fenfes in the 

 moft delightful manner. 



Thefe difcoveries are noble, and open to us a new fource of in- 

 veftigation into the wholfomenels or infalubrity of local fituations 

 in different countries, whether in the neighbourhood of large wood:,' 

 capacious lakes, and great rivers; or where the inhabitants are de- 

 flitute of fome, or all of thefe purifiers. If fuch is the grand provi/ion 

 made for our globe at large, may we not indulge a thought, that 

 it is difpenfed in a more liberal portion to thofe regions, whofe 

 climate feems to require it ? Dr. Hales computes, that refpiration 

 and perfpiration both together, in England, are equal to the quantity 

 of half the meat and drink which the people there daily take in; 

 this he eflimates at about thirty-nine ounces; but he rightly infers, 

 that it muft be far greater in hot climates ; as in hot climates therefore 

 the parents of putrefaftion, and of a corrupted atmo^here, are much 



[t] Sir John Pringle's Difcourfc, p. 26. 



more 



