This is a treatise showing the Aztecs' and kindred tribes' relationship to the Indo-Iranians and the place of the Nauatl or Mexican in the Aryan group of languages. Denison believed that all the American languages could be traced directly to the Old World, though he does not say they are all Aryan. The chief difficulty with those who have attempted to compare the American languages and races with those of other portions of the earth appeared to him to consist in the restriction of their field. This volume contains his conclusions on this subject and the manner in which he arrived at such conclusions.