When a boy, I have stood and wondered at the stupendous magnificence of the Mound-builders’ rude art, in crowning a beautiful hill with a throne for their Chieftain, or perhaps a temple to their god of nature, or possibly a sacrificial altar, on which to shed human blood to appease an irate divinity, or to dedicate the triumphal march of a conquering hero. Since a man, I have wandered among the thousands of mounds, from the Great Lakes to the Mexican Gulf, and have pondered among the unclassified tumuli on the plains of Texas that stretch away toward the Rio Grande, and have wondered if these are the watch-towers of a gigantic antediluvian prairie-dog contemporaneous with the _Deinosaurs_, or if they are the mute landmarks of a mysterious people who trafficked here while Cheops was building on the Nile. While modern science is endeavoring to classify the ethnic relations of the Mound-builders, it is also aware that that hypothesis alone will have credence, that accords best with the cumulative evidence of those most infallible guides, comparative craniology and philology. The science of craniology recognizes three, and sometimes four, kinds of skulls, determined by the ratio of length to the breadth; that is, the length of any skull being represented by 100, the “cephalic index” is the proportion of this 100 covered by the breadth. Skulls with a cephalic index between 74 and 78 are said to be _mesocephalic_, because this is the average of mankind. If the index is above 78, they are said to be _brachycephalic_; if below 74, they are _dolichocephalic_, or long-headed. The _dolichocephalic_, according to Prof. Retzius, are found in the eastern part of this continent, from Labrador through the Antilles to Paraguay. The _brachycephali_, or short heads, are found in the West, from Behring’s Strait, through Oregon and California, Mexico, Central America and Chili, to Terra del Fuego. It must be remembered that the terms “brachycephalic” and “dolichocephalic” are not absolute, but only relative as to length and breadth, for a dolichocephalic cranium may be actually shorter than a brachycephalic one.