Sect. II. Agriculture and Vegetation. 145 



ed with it, the mafs would cohere too 

 firmly together, and its furface would only 

 act ; whereas now the whole body acts. 

 It is in this way that I imagine the animal 

 and vegetable fubftances chiefly operate, 

 and not by entering into the compofition 

 of the nitre, as moft chymifls affert; be- 

 caufe nitre may be made by expofing alka- 

 line falls alone to the air ; for alkaline falts 

 attract acids, and are fo loofe as to fland in 

 need of no fermentation to open their 

 texture. The north wind is particularly 

 proper for the generation of nitre, be- 

 caufe that wind mufl bring more of the 

 nitrous acid along with it. That the cold 

 we feel from that wind, is chiefly owing 

 to a greater quantity of this acid, I think 

 is probable, though not demonftrable. The 

 winter months are particularly good, as 

 the north wind blows more in that feafon, 

 than in any other, and as there is lefs 

 heat to exhale the nitre during the opera* 

 tion. 



