I. AGRICULTURE AND RURAL ECONOMY. 329 



of sulphate of iron and finely divided iron pyrites, so small 

 an amount as J per cent, of the former being quite sufficient 

 to render a soil entirely unproductive. 



We can also ascertain by analysis whether a soil contains 

 an excessive portion of one or more matters otherwise useful 

 to vegetation, such as nitrate of potash, chloride of sodium, 

 etc. It appears to be the fact that all soils which contain 

 readily soluble salts, in quantities admitting of precise deter- 

 mination, are more or less unproductive, although the salt 

 may be a very effective fertilizer when applied in a weaker 

 solution. Thus a soil containing $ per cent., or even less, 

 of common salt hardly grows any crop ; this being the case 

 with land inundated by the sea. Such a proportion, indeed, 

 of any substance is much greater than could at any time be 

 applied with safety, while very minute quantities are fre- 

 quently of the utmost efficiency ; for so small a quantity as 

 fifty pounds of nitrate of soda, applied to an acre of grass- 

 land, or to wheat or barley, and thoroughly washed into the 

 soil, will produce a most marked effect in the darker green 

 color and greater luxuriance of the herbage compared with 

 the portion not so treated. One hundred pounds of ammo- 

 nia applied to an acre of land, in the shape of sulphate or of 

 chloride of ammonium, has been known to raise the average 

 produce of wheat twenty bushels, with a corresponding in- 

 crease of wheat straw ; and three hundred pounds of super- 

 phosphate of lime, of good quality, has been found to increase 

 the turnip crop in favorable seasons from six to ten tons per 

 acre. 



If a man wishes to make a living by farming, Dr. Voelcker 

 thinks that at least from three to five times as much of all 

 the more important fertilizers must be put annually upon the 

 land as is removed from it in the crops, a depreciation in the 

 cVop resulting when a materially less amount is applied. 

 21 A, Zondon, June, 1871,276. 



"allios" of the plains of southern feance. 



It is known to some of our readers that certain sandy soils 

 in the south of France, formerly perfectly barren and blown 

 about by the winds, have been reclaimed, by planting with 

 pines and firs, so as to become of much economical impor- 

 tance. A curious alteration has, however, taken place in the 



