42 DR. SCULEIDEN'S THEORY OF AGRICULTURE. 



lb. ; 



lu the first 5 years' course . . . 5,06 



In the second 5,15 



In the 6 years' course . . . . 9,83 



According to De Saussure, nitrogenous substances are per- 

 fectly decayed in 88 days. But supposing the nitrogen supplied 

 by the dung to be available for nutriment during the first year, 

 yet after repeated ploughing eveiy trace must have disappeared, 

 and there would be no supply but for that which is absorbed 

 from the air. Yet in the foregoing table we have the pro- 

 duction of 18-92 lbs. per acre in the second year, and 52*63 in 

 the fifth. If, then, 40 or 50 lbs. can be absorbed from the 

 atmosphere when no dung is present, it seems absurd to suppose 

 that 18 lbs. cannot be absorbed for the wheat and rye. 



If we refer to the table at page 39, we shall see that the 

 nitrogen was increased 37 per cent, in red clover grown in 

 quartzose sand or burnt clay, with distilled water, in the course 

 of 3 months only; while peas in 99 days gained 119 per cent., 

 and wheat 5 per cent. In the last experiment, red clover trans- 

 planted into tlie same soil gained in 2 months about 70 per cent. 



It remains only to inquire whether plants can derive sufficient 

 ammonia from the air. As before, in the consideration of car- 

 bon, it may be remarked that plants and animals are momentarily 

 giving out an immense quantity by the act of decomposition, 

 and though we find but little in the atmosphere and in variable 

 quantities, it must be recollected how easily and quickly it is 

 absorbed by every porous body and by water so as to be at once 

 available for nutriment. There is tiien a constant circulation of 

 this element as of cai'bon, and there are other sources, as volcanoes 

 and thunder storms, in which the hydrogen and oxygen arising 

 from the decomposition of water pass into nitrate of ammonia, 

 and the combination of free hydrogen with the carbon of the 

 atmosphere. Lastly, by a consideration similar to that which 

 was made with respect to carbon, it appears that -j'^ of a grain 

 of ammonia in every pound of water is sufficient for the exigen- 

 cies of vegetation, and there is perhaps no spring water in the 

 universe which contains so little. 



3. The quantity of sulphur and phosphorus is so small that 

 it is needless to enter into lengthened details. Peas, which yield 

 50 lbs. of nitrogen per acre, contain in tlie albumen 2 lbs. of 

 sulphur and 1 of phosphorus. If tlie time of vegetation is 

 spread over 120 days, and reckoning the height of the atmos- 

 phere at 3000 feet, only -5-4-Vo-o-o- of a grain of sulphuretted hydro- 

 gen and TrrFTiVo-o-o- of a grain of phosphuretted hydrogen per 

 cubic foot are requisite. 



