WATER IN AGRICULTURE. 177 



has been proved by careful experiments upon men 

 and animals, that pure distilled water, so vapid and 

 disagreeable to the taste, cannot be allowed to take 

 the place of impure spring water, without produc- 

 ing emaciation and actual disease. These are very 

 curious and suggestive facts. There is a wonderful 

 provision in nature by which the solvent powers of 

 water are prevented from being injurious to the 

 race. It will be understood that water is capable 

 of dissolving many compounds of the elementary 

 bodies, which are poisonous or prejudicial in their 

 influence, as well as those which are harmless or 

 beneficial. Among the metals, almost the only 

 one the oxide of which is harmless to the living 

 body, is the metal iron. This is held in almost all 

 natural waters. If the oxides of copper or lead 

 were as constantly present in our springs, lakes, 

 and rivers, as iron, our earth would be uninhabit- 

 able. The daily absorption into the system of mi- 

 nute quantities of metallic poisons is known to be 

 followed by consequences of a fearful kind. Why 

 are not these poisonous salts present in our natural 

 waters ? It is not owing to their insolubility, but 

 to the fact that they are very sparingly diffused 

 through the earth ; they are not present in most 

 soils. Iron is everywhere ; copper, lead, arsenic, 

 nickel, etc., are confined to specific localities, and 

 are away from the great centres of population. 



