LECTURES AND ESSAYS READ AT INSTITUTES. 381 



the period of growth. These experimenters used a thoroughness and consci- 

 entiousness which inspired the confidence of every person who examined their 

 experiments and studied their methods. The results at which they arrived by 

 a concurrence of "all their experiments, were that plants grown in the absence 

 of all combined nitrogen, except that contained in the seed, have no power of 

 taking up free nitrogen and combining it with other elements to form plant 

 tissue. This result is now accepted as a scientific fact by the great body of 

 agricultural chemists except the French school of Ville. 



FACTS THAT SEEM TO PAYOR THE FRENCH VIEW. 



There are many facts which seem to look in the direction of the views of 

 the French school. 1st. There must be a large supply of combined nitrogen 

 from some source to make good the heavy annual loss of combined nitrogen, 

 or else the supply of this necessary material for plant growth must diminish 

 year by year, and the starvation of the race from failure of plant growth from 

 want of combined nitrogen is only a question of time. This annual loss is 

 caused in many ways : (a) By combustion of nitrogenous materials when much 

 of the nitrogen escapes in the free form ; (b) in putrefactive decomposition of 

 organic substances when a part of the nitrogen escapes in free form, and more 

 in the form of ammonia; (c) enormous quantities of nitrates are yearly 

 formed in the soil and by the rivers washed into the sea and lost, so far as 

 land plants are concerned. It is estimated that the Nile daily pours the nitro- 

 gen equivalents of 1,100 tons of nitrate of potassium into the Mediterranean, 

 and the Mississippi 3,000 tons into the great gulf. 



The loss from all these sources is so great, that the world's supply of com- 

 bined nitrogen would have been sensibly diminished, if not exhausted, within 

 historic times, if nature did not in some way compensate this enormous waste. 



RESTORATIVE PROCESS. 



It is claimed that compensation is made in two ways : 1st. By the atmos- 

 pheric supply furnished in rain water in the form of ammonia and nitrates; 

 but this ammonia is itself the product of decomposition of previously existing 

 nitrogenous bodies, and is not an addition to the world's supply of combined 

 nitrogen, but evidence of waste of the original stock. The waste would be 

 made good only when we recover the whole of the ammonia contained in the 

 rain, but three-fourths of the rain falls into the sea and not on the land. 

 The atmospheric ammonia is a waste of the world's stock, and we recover in 

 the rain only 25 per cent of this waste. But the average atmospheric supply 

 of combined nitrogen is only eight pounds to the acre — an amount insufficient to 

 compensate for natural waste, and entirely inadequate to supply the wants of 

 any crop. 2d. Nitrification in the soil is adduced as one means of supplying 

 the necessary amount of nitrogen in the active form, and it is unquestionably 

 a chemical process of vast significance in agriculture. But nitrification is 

 mainly the oxidation of nitrogen compounds in the soil, and not a process of 

 accumulating free nitrogen to any great extent. It is, in fact, a step in the 

 direction of waste of combined nitrogen, for the investigations of Bret- 

 schneider, of Silesia, show that while nitrates in large amounts are annually 

 formed in every fertile soil, they do not remain and accumulate year by year, but 

 are annually washed out and disappear in the drainage water, and are finally 

 swallowed up by the all-devouring sea. 



Neither the atmospheric supply of combined nitrogen nor that supplied by 

 nitrification in the soil seem to be sufficient to supply the demands of grow- 



