192 RETROSPECT 



surface of the leaves of the meadow plants, there must also be 

 absorbed from the air above one part of ammonia. When we 

 calculate how much nitrogen different plants obtain from equal 

 surfaces of land, basing our calculations r»n known analyses, the 

 following results are obtained : 



1000 lbs. of carbon remove in nitrogen— 

 From meadow land, in hay 



These facts lead to certain conclusions of high importance to 

 agriculture. We observe, in fact, that the proportion of nitro- 

 gen absorbed, relatively to that of carbon, stands in a fixed rela- 

 tion to the surface of the leaves. 



1. Plants containing nearly all their nitrogen concen- 

 trated IN THEIR SEEDS, SUCH AS THE CEREALS, CONTAIN ALTO- 

 GETHER LESS NITROGEN THAN THE LEGUMINOUS PLANTS, PEAS AND 

 CLOVER. 



2. The crop of nitrogen from a meadow to which no 

 azotized manure has been given, is much greater than that 

 > rom a manured field of wheat. 



3. The crop of nitrogen in clover or in peas is much 

 greater than that of a highly-manured field of potatoes 

 or of turnips. 



Boussingault obtained in five years,. from his farm in Bechel- 

 bronn, Alsace, in the form of potatoes, wheat, clover, turnips, and 

 oats, 8383 carbon, and 250-7 nitrogen ; in the succeeding five 

 years,* 8192 carbon, 284*2 nitrogen ; in a third rotation of six 

 years,f 10949 carbon, 353*6 nitrogen ; or, in sixteen years. 

 27424 carbon, and 858*5 nitrogen ; or altogether, in the pro- 

 portion OF 1000 CARBON to 31*3 NITROGEN. 



• Eeet, wheat, clover, wheat, late turnips, oats, rye. 

 t Potatoes, wheat, clover, wheat, late turnips, peas, rye. 



