44 CHYMISTRY APPLIED TO AGRICULTURE. 



crumbles, and effloresces. The decomposition of marl 

 may be hastened by frequently turning it, so as to allow 

 the air free access to the lime ; and this method is gene- 

 rally practised by those who employ marl as a manure. 

 The same questions may be proposed in regard to imper- 

 fectly carbonated lime, as to the oxide of iron. 



When M. Fellenberg wished to verify his principles of 

 cultivation upon his estate of Hofwyl, he had his land 

 broken up to the depth of three or four feet, and it pro- 

 duced nothing till the end of two or three years. 



These facts, and many others which I could cite, prove 

 that it is necessary for earths, in order to possess great 

 fertilizing powers, to be saturated with all the principles 

 which they can imbibe from the atmosphere. Thus those 

 which, by the depths of their beds, have been constantly 

 secluded from the action of the air, will require to be 

 exposed to it a long time before becoming fertile. Those 

 who are engaged in agriculture know this fact, and ex- 

 press it by saying that the air deposits its fructifying prin- 

 ciples upon the earth. They use the expressions, — " The 

 soil is not made enough ; is not ripe enough ; is not aired 

 enough," &c. This understanding of the subject is not 

 very exact, but sufficiently so to direct their practice. 



When, by digging or deep ploughing, the mould has 

 been mixed with these unsaturated earths, it ought to be 

 stirred at long intervals by the plough or pick-axe, before 

 being sowed. By presenting all the parts successively to 

 the action of air and water, they are enabled to imbibe 

 from them those principles in which they are deficient ; 

 and thus the same effect is produced upon them, as is 

 wrought upon marl or the black ferruginous earths by a 

 longer exposure^ after they have been taken from their 

 beds. 



ARTICLE VII. 



Of the Analysis of Arable Soils. 



Though experience and long observation may enable an 

 agriculturist to become acquainted with the nature and 

 degree of fertility of each part of his land, it will in most 

 cases be convenient for him to acquire this knowledge by 

 shorter and more direct methods. 



