19« RETROSPECT. 



1st year. 2d Year 3d, 4th, 5th, 6th Years. 7th Year. 8th Year. 9th Year. 



Manured. Manured. 



Turnips Barley with Lucern. Potatoes. Wheat. Barley. 

 Lucern. 



Six years after manuring, after the supply of ammonia and 

 manure containing nitrogen, after four succeeding crops of clover, 

 and after a crop of barley and one of oats, the soil of Bingen 

 yields rich crops of potatoes, wheat, and barley, and these suc- 

 ceed each other at a time when, according to our assumption, the 

 manured field in Alsace was to be viewed as completely ex- 

 hausted of its nitrogen. Can it be conceived that the ammonia 

 of the manure could, after the lapse of 8 — 9 years, furnish the 

 nitrogen to the crops of wheat and barley ? But even admitting 

 this to be the case, we have then to inquire whence do the corn- 

 fields in Hungary, in Sicily, or in the vicinity of Naples, receive 

 their nitrogen, for these fields have never been manured ? Are 

 we actually to believe that the nutrition of plants in the fields 

 of moderate climates is subject to different laws from those 

 governing the warmer and tropical regions ? 



In Virginia the annual crop of nitrogen in wheat amounted to 

 22 lbs. an acre, on the smallest calculation, or in 100 years to 

 2200 lbs. If we were to suppose that this nitrogen was fur- 

 nished by the field, each acre must have contained it in the form 

 of hundreds of thousand pounds of animal excrements ! 



The whole population of Limousin subsist upon milk and 

 sweet chestnuts, the production of which, being unattended with 

 trouble, is ascribed by Dupin as the cause of their low state of 

 intellect. Without being subjected to any system of farming, 

 this district produces enormous quantities of the constituents of 

 the blood, the nitrogen of which cannot have been produced from 

 manure. 



For centuries, in Hungary, wheat and tobacco have been cul- 

 tivated on the same field, without any supply of nitrogen. Is it 

 possible that this nitrogen can have had its origin in the soil ? 

 Our forests of beeches, chestnuts, and oaks, become covered with 

 leaves every year ; the leaves, sap, the acorns, chestnuts, cocoa- 

 nuts, the fruit of the bread-tree, are rich in nitrogen. This 

 nitrogen is not contained in the soil, nor is it conveyed to the 



