11*2 PEINXIPLES OF GARDENING. [CH. II. 



always chalk, often to the amount of 50 per cent. They 

 leaiiDjfrom experience, that the marl of one district is 

 most beneficial to their hea^T soils ; that of a second 

 district is productive of most benefit upon light land : 

 yet they are ignorant, in the first instance, that the 

 first marl contams silica or sand ; that the second has 

 alumina, or clay, as a component, and if a new pit of 

 marl is opened, they have to wait the result of some 

 years' practice before they ascertain its quality. The 

 chemist can inform them in an hour, and this 

 naturally leads to a consideration of the indications 

 of a soils steiility or productiveness. 



Xo soil is absolutely barren — not an instance is 

 known of land, penetrable by the spade or by the 

 ploughshare, that ^ill not support some species of 

 plant seniceable to man. By the use of the term 

 barren, therefore, in these pages, I intend no more 

 tlian that the soil, in its present state, "svill not 

 repay its cultivator for his expenditui*e of money 

 and labour. 



By the term fertility. I intend the exact converse. 

 Wlien a soil is spoken of as fertile, it must not be 

 understood (unless so stated) that it is rich and 

 largely remunerating ; but merely that it is suffi- 

 ciently productive to reward its cultivator for his 

 expenditure, and to induce him to contmue the appli- 

 cation of his capital upon it. 



Now the natural indications which mav enable the 



