JoLY — An Estimate of the Geological Age of the Earth. 



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. Tte atstraetion 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 actirity in the part arising from diminished solar heat, very 



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



4. TJnder-estimate 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, &c. 



6. Under-estimate of the mass of sodium now in the ocean or over-estimate of that delivered in 



the river-supply to the ocean. 



7. Over-estimate of sodium supplied to the ocean by a probable primeval accelerated 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 ot sodium to the sea otherwise than by normal river 



supply, as volcanic emissions ; denudation of inland E,ock Salt deposits into the ocean by brine 

 springs, &o. 



3. Increased meteorological activity in the past arising from very different distribution of land 



and water, glacial periods or other causes. 



4. Over-estimate 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 and river 

 water, &c. 



6. Over-estimate of the mass of sodium now in the ocean or under-estimate of that delivered 



in the river-supply to the ocean. 



7. TJnder-estimate of sodium supplied to the ocean by a probable primeval accelerated denu- 



dation. 



