66 
Joty—An Estimate of the Geological Age of the Earth. 
AppenpDix 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 :— 
Ilo 
The abstraction of sodium chloride from the ocean by evaporation of sea water in bays 
or inlets cut off from the sea. 
. The deposition of sodium chloride as a constituent of submarine sediments and deposits. 
. Diminished meteorological activity in the part arising from diminished solar heat, very 
different distribution of land and water, glacial periods, or other causes. 
. Under-estimate of the supply of sodium chloride to the rivers by rainfall. 
. 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, &e. 
. Under-estimate of the mass of sodium now in the ocean or over-estimate of that delivered in 
the river-supply to the ocean. 
. Over-estimate of sodium supplied to the ocean by a probable primeval accelerated denudation. 
Those tending to render the estimate a maximum are :— 
. The supply of sodium to the ocean by direct marine solution of coast materials and sediments. 
. 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, &c. 
Increased meteorological activity in the past arising from very different distribution of land 
and water, glacial periods or other causes. 
. Over-estimate of the supply of chloride of sodium to the rivers by rainfall. 
. 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. 
. Over-estimate of the mass of sodium now in the ocean or under-estimate of that delivered 
in the river-supply to the ocean. 
. Under-estimate of sodium supplied to the ocean by a probable primeval accelerated denu- 
dation. 
