245 



agricultural industry gradually declines. Coffee 

 and cotton trees progressively take place on 

 many spots of the cacao, of which the lingering 

 harvests weary the patience of the cultivator. 

 It is also asserted^ that the new plantations of 

 cacao are less productive than the old; the trees 

 do not acquire the same vigour, and yield later 

 and less abundant fruit. The soil is still accused 

 of being exhausted ; but we think it is rather 

 the atmosphere, that is changed by the progress 

 of clearing and cultivation. The air, that re- 

 poses on a virgin soil covered with forests, is 

 loaded with humidity, and those gaseous mix- 

 tures, that serve for the nutriment of plants, and 

 arise from the decomposition of organic sub- 

 stances. When a country has been long sub- 

 jected to cultivation, it is not the proportions 

 between the azot and oxygen that vary. The 

 constituent bases of the atmosphere remain un- 

 altered ; but it no longer contains, in a state of 

 suspension, those binary and ternary mixtures of 

 carbon, azot, and hydrogen, which a virgin soil 

 exhales, and which are regarded as a source of 

 fecundity. The air, purer and less charged with 

 miasmata and heterogeneous emanations, be- 

 comes at the same time dryer. The elasticity 

 of the vapours undergoes a sensible diminution. 

 On land anciently cleared, and consequently 

 little favourable to the cultivation of the cacao- 

 tree, for instance in the West India islands, the 



