The Dutch anatomist, Camper, distinguishes the Human Family by the facial angle, ranging from eighty degrees, in the European, down to seventy degrees, in the Negro.[131] This attempt was continued by Virey, who divides Man into two species: the first with a facial angle of 85° to 90°, including Caucasian, Mongolian, and copper-colored American; and the second with a facial angle of 75° to 82°, including dark-brown Malay, blackish Hottentot and Papuan, and the Negro. Prichard, whose voluminous works constitute an ethnological mine, finds, chiefly from the skull, seven varieties, which he calls (1.) Iranian, from Iran, the primeval seat in Persia of the Aryan race, embracing the Caucasian of Blumenbach with some Asiatic and African nations; (2.) Turanian or Mongolian; (3.) American, including Esquimaux; (4.) Hottentot and Bushman; (5.) Negro; (6.) Papuan, or woolly-haired Polynesian; (7.) Australian. The same industrious observer finds three principal varieties in the conformation of the head, corresponding respectively to Savage, Nomadic, and Civilized Man. In the savage African and Australian the jaw is prolonged forward, constituting what he calls, by an expressive term, _prognathous_. In the nomadic Mongolian the skull is pyramidal and the face broad. In Civilized Man the skull is oval or elliptical. But the naturalist records that there are forms of transition, as nations approach to civilization or relapse into barbarism. Thus does the Human Skull refuse any definitive answer. There are varieties of skull, as of color; but the question remains, to what extent they attest original diversity. Equally vain is the attempt to obtain a guide in the form of the human pelvis. But every such attempt and its failure have their lesson. There remains one other criterion: I mean Language. And here the testimony is such as to disturb all divisions founded on Color or Skull; for it is ascertained that people differing in these respects speak languages having a common origin. The ancient Sanscrit, sometimes called the most elaborate of human dialects, has yielded its secret to philological research, and now stands forth the mother tongue of the European nations. It is difficult to measure the importance of this revelation; for, while not decisive on the main question, it increases our difficulty in accepting any postulate of original diversity.[132]