170 FIRESIDE SCIENCE. 



render it unfit as a beverage for man or beast. It 

 is well known that in the gradual decomposition 

 of animal and vegetable substances at or near the 

 surface of the earth, under certain conditions, 

 nitrogenous compounds are formed. The nitre 

 earths found under old buildings result from these 

 changes. It is, however, quite difficult to under- 

 stand the precise nature of the chemical transfor- 

 mations which produce them. In the waters of 

 a large number of wells in towns and cities, and 

 also in the country, the nitrates are found in con- 

 siderable quantities. The salts form at the surface 

 in warm weather, and being quite soluble are car- 

 ried with the percolating rain water into the wells. 

 Hence it will be understood how important it is to 

 locate wells away from all contaminating influences. 

 It has long been a matter of surprise to me that 

 instances of impure water are so often found in the 

 rural districts, among those who are not confined 

 to the narrow limits of city lots. In an experience 

 of many years as consulting chemist, I have had 

 a larger percentage of examinations to make of 

 water brought from country homes, than from any 

 other source. The result of these examinations 

 has proved that great carelessness is manifested 

 in allowing sink drains, cess-pools, and excrementi- 

 tious deposits to exist in close proximity to the 

 water supply, and serious illnesses have been 



