The essay of Count Gobineau is eminently practical and useful in its design. He views the various races of men rather as a historian than a naturalist, and while he leaves open the long mooted question of _unity_ of origin, he so fully establishes the _permanency_ of the actual moral, intellectual, and physical diversities of races as to leave no ground for antagonists to stand upon. Whatever _remote causes_ may be assigned, there is no appeal from the conclusion that white, black, Mongol, and other races were fully developed in nations some 3000 years before Christ, and that no physical causes, during this long course of time, have been in operation, to change one type of man into another. Count Gobineau, therefore, accepts the _existing_ diversity of races as at least an _accomplished fact_, and draws lessons of wisdom from the plain teachings of history. Man with him ceases to be an abstraction; each race, each nation, is made a separate study, and a fertile but unexplored field is opened to our view. Our author leans strongly towards a belief in the _original diversity_ of races, but has evidently been much embarrassed in arriving at conclusions by religious scruples and by the want of accurate knowledge in that part of natural history which treats of the designation of _species_, and the laws of _hybridity_; he has been taught to believe that two distinct species cannot produce perfectly prolific offspring, and therefore concludes that all races of men _must_ be of one origin, because they are prolific _inter se_. My appendix will therefore be devoted mainly to this question of species. A. Our author has taken the facts of Dr. Morton at second hand, and, moreover, had not before him Dr. Morton's later tables and more matured deductions; I shall therefore give an abstract of his results as published by himself in 1849, with some comments of my own. The figures represent the internal capacity of the skull in cubic inches, and were obtained by filling the cavity with shot and afterwards pouring them into an accurately graduated measure. It must be admitted that the collection of Morton is not sufficiently full in all its departments to enable us to arrive at the absolute capacity of crania in the different races; but it is sufficiently complete to establish beyond cavil, the fact that the crania of the white are much larger than those of the dark races. His table is very incomplete in Mongol, Malays, and some others; but in the white races of Europe, the black races, and the American, the results are substantially correct. I have myself had ample opportunities for examining the heads of living negroes and Indians of America, as well as a considerable number of crania, and can fully indorse Dr. Morton's results. It will be seen that his skulls of American aborigines amount to 338. _Table, showing the Size of the Brain in Cubic Inches, as obtained by the Measurement of 623 Crania of various Races and Families of Man._