The duke also tried to show that there were no distinctive epochs of stone, bronze, and iron, by adducing the fact that some stone implements are found even in some high civilizations.

This is indeed a fact.

We find some few European peasants to-day using stone mallet-heads; but this proves simply that the old stone mallet-heads have survived as implements cheap and effective.
The argument from Comparative Ethnology in support of the view that the tendency of mankind is upward has received strength from many sources.
Comparative Philology shows that in the less civilized, barbarous, and savage races childish forms of speech prevail--frequent reduplications and the like, of which we have survivals in the later and even in the most highly developed languages.

In various languages, too, we find relics of ancient modes of thought in the simplest words and expressions used for arithmetical calculations.

Words and phrases for this purpose are frequently found to be derived from the words for hands, feet, fingers, and toes, just as clearly as in our own language some of our simplest measures of length are shown by their names to have been measures of parts of the human body, as the cubit, the foot, and the like, and therefore to date from a time when exactness was not required.
To add another out of many examples, it is found to-day that various rude nations go through the simplest arithmetical processes by means of pebbles.