In the Geological Magazine for August I gave the major limit to the period of time we can assign to the geological age of the Earth by the solvent-denudation method, when it is assumed that all the chlorine of rivers is derived directly from the ocean, and that all such chlorine (falling, as assumed, in rain) carries its full complement of sodium from the ocean. The major limit with these assumptions is 141 million years. A second estimate is given on the more moderate assumption that one-third the amount of chlorine in rivers is derived from the sea and brings with it its full equivalent of sodium; this affords 105 millions of years as the age. Finally, there is the original estimate based on a 10 per cent. deduction from the chlorine of rivers as rain-borne, affording 96 millions of years.