Soil. 21 



from soils, which were originally sterile, and which would 

 soon revert to their former state of barrenness, without the 

 greatest industry, and the most unwearied attention ( 6< *). 



In the management of sandy soils, three rules are to be 

 observed : I. Never to pick off any small stones that may 

 be found in them, as they answer many valuable purposes : 

 they shelter the young plant in bad weather ; they preserve 

 moisture, and prevent the crops from being burnt up by 

 scorching heats; they hinder the evaporation of the enrich- 

 ing juices ; and, by these means, greatly assist the progress 

 of vegetation ( 63 ). 2. Frequently to renovate the strength 

 of such soils, by laying them down with grass-seeds, and 

 pasturing them for a few years, as they are apt to be exhaust- 

 ed by ploughing, if corn crops are too frequently repeated; 

 and, 3. When farm-yard dung is applied to this description 

 of soil, always to give it in a state of compost, with a view 

 of adding to the tenacity of the soil, and of preventing the 

 manure from being dissipated in a dry season, or washed 

 down by rain ( 64 ). 



It may be added as a general maxim, that the fertility of 

 sandy, or siliceous soils, is in proportion to the quantity of 

 rain that falls, combined with the frequency of its recur- 

 rence. As a proof of this, in the rainy climate of Turin, 

 the most prolific soil has from 77 to 80 per cent, of siliceous 

 earth, and from nine to fourteen of calcareous ; whereas in 

 the neighbourhood of Paris, where there is much less rain, 

 the silex is only in the proportion of from 26 to 50 per 

 cent., in the most fertile parts ( 65 ). 



2. Gravel. Gravelly soils differ materially from sandy, 

 both in their texture, and modes of management. They are 

 frequently composed of small friable stones, sometimes of 

 flinty ones ; but they often contain granite, limestone, and 

 other rocky substances, partially, but not very minutely de- 

 composed. Gravel, being more porous than even sand, is ge- 

 nerally a poor, and what is called, a hungry soil, more espe- 

 cially when the parts of which it consists are hard in sub- 

 stance, and rounded in form ( 66 ). Gravelly soils are easily 

 exhausted ; for the animal and vegetable matters they con- 

 tain, not being thoroughly incorporated with the earthy 

 constituent parts of the soil, (which are seldom sufficiently 

 abundant for that purpose), are more liable to be decom- 

 posed by the action of the atmosphere, and carried off by 

 water ( 6? ). 



Gravelly soils are improved by draining, if they are trou- 

 bled with springs, which is sometimes the case; by plough.- 



