288 AN ESTIMATE OF THE GEOLOGICAL AGE OF THE EARTH. 



Mass of ocean ^ L460X lO^Mons. 



Mass of NaCl in ocean 39,782 X IQi- tons. 



Mass of Xa in ocean 1 5, 627 X IQi'^ tons. 



Mass of CI combined with Na in ocean 24, L55 X lO'- tons. 



Mass of K2SO4 in ocean 1,260 X lO^^ tons. 



Mass of K in ocean 565 X 10^- tons. 



Mass of MgCla in ocean 5,568 X 10^^ tons. 



Mass of CI combined with Mg in ocean 4, 161 X 10^^ tons. 



Annual river discharge into oceans 6,524 cubic miles. 



Mass of so(hum in a cubic mile of river water 24,106 tons. 



Annual river supply of Na 15,727 X 10* tons. 



Annual (calculated) Na.p discharge of rivers 21 X 10' tons. 



Annual (calculated) K.^O discharge of rivers 7.3 X 10" tons. 



Estimated bulk of siliceous sedimentary detrital rock .. =layer 1.1 mile thick over 



land. 



Soda percentage of primitive rock 3.61. 



Potash percentage of primitive rock 2.83. 



Mean soda percentage of sedimentaries 1.47. 



Mean potash percentage of sedimentaries 2.49. 



Appendix II. 



The errors possibly affecting the foregoing method of estimating 

 geological time are of both signs, and are here enumerated. 

 Those tending to render the estimate a minimum are: 



1. The abstraction of sodium chloride from the ocean by evaporation of sea water 

 in bays or inlets cut off from the sea. 



2. The deposition of sodium chloride as a constituent of submarine sediments and 

 deposits. 



3. Diminished meteorological activity in the past arising from diminished solar 

 heat, very different distribution of land and water, glacial periods, or other causes. 



4. Underestimate of the supply of sodium chloride to the rivers by rainfall. 



5. Diminished river supply of sodium in the past due to lithological differences in 

 rocks and soils exposed to denudation or diminished amounts of organic acids, etc. 



6. Underestimate of the mass of sodium now in the ocean or overestimate of that 

 delivered in the river supply to the ocean. 



7. Overestimate of sodium supplied to the ocean l)y a probable primeval acceler- 

 ated denudation. 



Those tending to render the estimate a maximum are: 



1. The supply of sodium to the ocean by direct marine solution of coast materials 

 and sediments. 



2. Certain sources of supply of chloride of sodium to the sea otherwise than by 

 normal river supply, as volcanic emissions, denudation of inland rock salt deposits 

 into the ocean by brine springs, etc. 



3. Increa.'ied meteorological activity in the past arising from very different distri- 

 bution of land and water, glacial periods, or other causes. 



4. Overestimate of the supply of chloride of sodium to the rivers by rainfall. 



5. Increased river supply of sodium in the past due to lithological differences in 

 the rocks and soils exposed to denudation or to chemical effects of carbonic acid in 

 rain or river water, etc. 



6. Overestimate of the mass of sodium now in the ocean or underestimate of that 

 dehvered in the river supply to the ocean. 



7. Underestimate of sodium supplied to the ocean by a probable primeval acceler- 

 ated denudation. 



