i66 



PRINCIPLES OF STRATIGRAPHY 



This is 39.50 grams in one thousand liters of rain water. At 

 Troy, New York, the mean chlorine content of the rain water for 

 one year was found to be 0.00164 permille, or 1.64 grams per 1,000 

 liters. 



At Lincoln, New Zealand, the impurities of the rain water were 

 found by Gray to average during two years as follows : 



Impurities of Rain Water. 



Permille 



CI o . 00774 



SO3 0.00201 



N in NH3 0.00012 



N in nitrates o . 00014 



N albuminoid o . 00009 



Other matter 0.01350 



Total dissolved matter 0.02360 



The following solids, in pounds per acre per annum, have been 

 determined as brought by the rain in various localities. (Clarke- 

 4:46-47.) 



From the soil the rain water takes CO, and humus acids derived 

 from both living and decaying vegetation, and these, with the acids 

 derived from the atmosphere, will exercise a solvent power upon 

 the rocks through which the water passes. Several of them are 

 good solvents of silica, and the streams passing through bogs are 

 generally rich in this constituent. Thus the Ottawa drains a region 

 occupied chiefly by crystalline rocks, covered by extensive forests 

 and marshes, and its percentage of silica is 33.7 of the total in- 

 organic solids.f 



*Average of five years. 



t For a full discussion of the Geological action of the Humus Acids see Julien 

 (17). For a correlation between compositions of river water and source of the 

 water see Hanamann (12). 



