ACTION OF THE SOIL ON PLANTS. 157 



cesses : by tillage, by amendments, by manure, and by 

 rotation of crops. These follow each other in natural 

 succession. Man first begins by cultivating the earth ; 

 he next endeavors to ameliorate the soil, in order to ren- 

 der it more propitious to the produce he wishes to raise. 

 After having yielded a certain number of crops, he ob- 

 serves that the earth is exhausted of its nutritive princi- 

 ples, and that the crops are poor and meagre. He finds 

 the means of renovating these principles by manuring 

 the land ; and, when manure falls short, he discovers 

 that a judicious system of cropping answers, in a great 

 measure the same purpose. , 



The principal object of tillage is to break and crumble 

 the earth, in order that the roots of young plants may ea- 

 sily penetrate into it ; to expose every part of the soil 

 successively to the action of the air, so that such of the 

 earths or metals, as are destined to be converted into salts 

 by the action of the oxygen of the atmosphere may be 

 brought into contact with it, as well as such remains of 

 organic bodies as can be dissolved only by oxygen. Va- 

 rious implements of husbandry are employed for this pur- 

 pose ; and it is a continual object of dispute, between 

 the agriculturists of different countries, which answers 

 the purpose best. 



Emily. But is not the plough the instrument univer- 

 sally used in all civilised countries ? 



Mrs. B. Most commonly ; but the plough itself is of 

 various descriptions, and you have observed the peasantry 

 of Tuscany frequently employing the spade, an implement 

 which we reserve for garden culture. They are, indeed, 

 bound by the tenure on which they hold their land to dig 

 it up every third year. The spade undoubtedly performs 

 the operation of turning and subdividing the earth more 

 completely than the plough, but at a much greater ex- 

 pense of labor ; and it is an instrument adapted only to 

 light and homogeneous soils, for if the earth be of unequal 

 tenacity, or interspersed with stones, it cannot be used. 

 The pickaxe may in those cases be substituted, as it is 



863. By what different processes may soils be improved'? 864. 

 What is the succession used in agriculture 1 ? 865. What may be a sub- 

 stitute for manuring! 866. What is the principal object of tillage 7 

 867. What is observed of the peasantry of Tuscany! 868. What 

 Comparison is made between the use of the spade and the plough! 869. 

 In hard soils what instrument is substituted for the spade! 

 14 



