76 



THE FARM WATER SUPPLY 



the rain, which washes the atmosphere free of this gaseous sub- 

 stance, that escapes into it from every fire and every piece of 

 decaying animal or vegetable substance. The ammonia pres- 

 ent in water is usually spoken of as free ammonia in order to 

 distinguish it from ammonia which the chemist obtains from 

 the nitrogen in the soluble organic matter by means of suitable 

 chemicals and calls albuminoid ammonia. Ammonia and sol- 

 uble organic matter containing nitrogen are rapidly changed in 

 the soil by certain micro-organisms into nitrites and nitrates. 

 These latter comuounds, especially nitrites, are also formed in 

 the atmosphere by electrical discharges and therefore occur in 

 rain especially after or during thunder showers. Nitrites and 

 nitrates are very necessary to the life of plants, however, and 

 consequently, under natural conditions of soil and moisture, 

 they will be absorbed by plant-roots as fast as formed. Hence 

 unpolluted springs show no nitrites nor nitrates and only minute 

 quantities of free and albuminoid ammonia. Heavily man- 

 ured fields in the vicinity of a spring may cause the presence 

 of nitrates and nitrites as well as an increase of chlorine in the 

 water, because there is often a larger supply of them than the 

 crops can handle, and they are easily leached from the upper 

 layers of soil beyond the reach of plant-roots. Leaves or saw- 

 dust not uncommonly to be found in springs, are pretty sure to 

 increase the amount of albuminoid ammonia above what it 

 would be if the spring were clean. The following table will 

 better explain these variations. 



NITROGENOUS MATTER IN GOOD GROUND WATERS. PARTS IN 100.000. 



* Walls of spring are of brick and cement, causing lime in water and high 

 solid residue. 



1 Free from contamination. Residue did not blacken when burned. 



2 Spring near a corn-field. College farm. 



* Spring contained leaves. Residue blackened when burned, showing pres- 

 ince of organic matter. 



