CLASSIFICATION. 225 



the quantity of sand is as low as 30 per cent. With less than 30 

 per cent, oats will thrive. Wheat may still be advantageously cul 

 tivated upon lands that contain from 40 to 50 per cent, of sand ; 

 beyond this term, when the soil contains from 50 to 60 per cent, of 

 sand, it is more advantageous to grow barley. Such a soil will not 

 be completely pulverized by reiterated ploughing, as will that which 

 contains a larger proportion of silicious matter, and it does not be- 

 come hard and cracked under drought like lands that are more 

 essentially clayey, because it retains a sufficiency of moisture ; it is 

 equally well adapted for trefoil of all kinds, for tubers, for plants 

 with tap roots, and for many other crops of great marketable value, 

 such as cabbage, flax, tobacco, &c. It is almost always accessible, 

 a circumstance which allows of the greatest care being bestowed 

 upon the crops which are raised upon it. In soils which yield on 

 washing from 60 to 80 per cent, of sand, we cannot reckon securely 

 on the success of wheat. At 70 of sand, it ceases to be well adapted 

 to the cultivation oi this grain, except with especial precautions ; but 

 it is still well adapted to barley, and it is in such a soil especially 

 that rye succeeds best. 



Land with such a dose of sand is always easily labored, but it is 

 more apt to be overrun by foul weeds than a soil that is decidedly 

 argillaceous. Manures are speedily consumed in it for the reason 

 already given ; it is, therefore, advantageous to manure such land 

 frequently, laying on less dung at a time. A soil having 75 per cent, 

 of sand, is qualified by Thaer as an oat soil, and even up to 85 per 

 cent, of sand it may be regarded as suitable to this grain ; this term 

 passed, nothing but rye or buckwheat ought to be sown upon it, 

 and that only after it has had a sufficient dose of manure. The re- 

 iterated ploughings which some of these sandy soils require to get 

 rid of the foul v eeds which rush up in such quantities upon them, 

 sometimes rendt them so open that rye will not succeed. The best 

 course is then to 'ay them down in grass, and allow them to become 

 consolidated by -st. 



It is extremely diff.cult, at least in this climate of ours, to make 

 any thing of soils that contain 90 per cent, of sand ; in times of 

 drought they become true moving sands. As we have already shown, 

 calcareous matter may replace silicious sand in the part which it 

 plays in an arable soil ; like sand, calcareous matter tends to de- 

 stroy the strong cohesion of the particles of clay : but it appears that 

 chalk or lime, especially when it is in a state of minute subdivision, 

 besides this effect, really contributes to the amelioration of wheat 

 lands. 



The feiUowing table comprises the results obtained by Thaer and 

 Einhoif. I must observe, however, and from causes which have 

 been already explained as influencing the determination of the humus, 

 that this substance is evidently estimated at much too high a figure 

 in several of these analyses, which deserve to be made anew under 

 the precautions that are now familiarly known. 



