36 MISCELLANEOUS FARM SUBJECTS 



service in aiding one to select a proper source of water supply. No 

 water is perfectly pure, and nature does not intend man to use chem- 

 ically pure water, for certain salts and metals in solution are neces- 

 sary for the human body. On the other hand, there are some kinds 

 of pollution which are undesirable and even dangerous. The most 

 common forms in which this pollution comes are in the form of 

 lime or magnesia, which makes the water hard. There is no great 

 danger in drinking hard water, so far as medical knowledge goes, 

 although a person accustomed to soft water will probably suffer 

 temporary discomfort on changing to the other. The chief objection 

 to hard waters is in the large amount of soap needed in using them, 

 the disagreeable effect of those waters on the skin, and the deposits 

 formed by precipitation in cooking or in the laundry. 



The proportion of matter ground water will have in solution 

 depends upon the quantity of soluble substances with which it comes 

 in contact during its passage from the clouds, through the air, and 

 the soil, and the amount of soluble material plant roots will absorb 

 as the water percolates among them. More important than the 

 amount of matter dissolved in the water is the composition of the 

 matter. The best evidence of the origin of the matter held in solu- 

 tion by the water is obtained by determining the amount of chlorine 

 present. This element is one of the two which forms common salt, 

 and is almost invariably present in a natural ground water. The 

 proximity of cultivated fields will modify the amount of chlorine 

 naturally present in a spring water, owing to the application of 

 fertilizers. It is always safe to have a test made of the water before 

 using it for household purposes. (N. H. C. B. 53; Cornell Univ. 

 Reading Course 29.) 



To judge the healthfulness of a water after knowing something 

 about the origin of its soluble constituents, the most stress is laid 

 upon the relative quantities of four different compounds of nitrogen, 

 an element occurring in all animal and vegetable tissues, as well as 

 forming four-fifths of the atmosphere. It occurs in water in the 

 form of ammonia, soluble organic matter and two classes of com- 

 pounds, called respectively nitrites and nitrates. The ammonia in 

 unpolluted spring-water is due mainly to the rain, which washes the 

 atmosphere free of this gaseous substance, that escapes into it from 

 every fire and every piece of decaying animal or vegetable substance. 

 The ammonia present 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 called albuminoid ammonia. Ammonia and soluble 

 organic matter containing nitrogen are rapidly changed in the soil 

 by certain micro-organisms into nitrites and nitrates. These latter 

 compounds, 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 me of plants, however, and consequently, under natural con- 

 ditions of soil and moisture, they will be absorbed by plant-roots 

 as fast as formed. Hence unpolluted springs show no nitrites nor 



