202 MASSACHUSETTS UOllTICULTDKAL SOCIETY. 



witli a considerable margin ; but we may perhaps allow tluit from 

 ten to twelve pounds of nitrogen per acre will be provided for the 

 crops or, rather, carried down to tlie soil ever}' year ; some of it, 

 hov\ever, in the cold season when no crop is growing. An acre's 

 crop of clover requires about 100 lbs. of nitrogen ; of Indian corn, 

 80 lbs. ; of timothy, 45 lbs. ; of potatoes, 44 lbs. Therefore the 

 supply in the rain is far from suQicient, even if all of it should 

 come at the right time, and be at once taken up by vegetation ; 

 but such complete use of it is not at all probable. 



So much for the nitrogen that the crops may possibly gather 

 from compounds of nitrogen in the atmosphere. Now, while still 

 affirming that the principle is well established that there is, in the 

 living plant, no power to cause nitrogen to enter into chemical 

 combination, it must be granted that there seem to be evidences of 

 such a power working, in quiet and unobtrusive ways, outside of 

 the plant, or quite independently of its vital activity. Two discover- 

 ies in this direction have been made by Berthclot, an eminent 

 French chemist. lie has shown, first, that through the electrical 

 relations existing between the earth and the atmosphere, and es- 

 pecially- in the presence of certain very common vegetable products, 

 nitrogen is quietly persuaded into chemical combination. But we 

 have not, as yet, the least idea how much or how little nitrogen is 

 likely to be thus made available to vegetation. The importance of 

 this discovery seems small in comparison with the later one, made 

 known only last year. In this Berthelot found that free nitrogen 

 is absorbed by chiy — whether pure or mixed with sand — and is 

 converted into some form of combination that is neither ammonia 

 nor nitrate. When a pot of ordinary loam was exposed freel}' to 

 the air, so that it might take possession of all the combined nitrogen 

 that could reach it in the rain or dew, or by direct absorption of 

 ammonia, it was found to contain considerably more nitrogen, 

 taken up, by this newly discovered method, from the free nitrogen 

 of the air, than was collected by all the other methods ; the action 

 of the clay appearing to be entirely independent of the combined 

 nitrogen already existing in the air. It was found, further, that 

 this absorption of free nitrogen was dependent upon the coopera- 

 tion of minute living organisms, called bacteria; for if the soil is 

 previously sterilized, as it is called, by heating it up to the boiling 

 point of water, when all such organisms are killed, and it is then 

 exposed only to air lillcicd through cotton, through which no fresh 



