Facial goniometer, which measures dimensions of the skull. This illustration is from Crania Americana; or, A Comparative View of the Skulls of Various Aboriginal Nations of North and South America by Samuel George Morton (1799-1851), an American physician and natural scientist. Morton believed that skull capacity determined intelligence, and he used his craniometric measurements to support the idea of a racial hierarchy with Caucasians at the top and Africans at the bottom. His measurements of cranial volume were used as evidence for racial stereotypes. His results were published in three volumes between 1839 and 1849: the Crania Americana, and Crania Aegyptiaca.