XXXIII.

_Antiquity of the human species._--This problem is most likely to be worked through the phænomena of language. When determined it will give precision to the _recent period_ of the geologist, converting it from a _relative_ into a conventionally _absolute_ epoch.

The average rate at which languages change is capable of being approximated.

The _maximum_ difference, at a given period, between two or more languages is also capable of being approximated.

The original unity of the species is a postulate.

The _minimum_ amount of time necessary for the _maximum_ amount of difference is the measure of the shortest admissible _recent period_.