But, if history is indispensable to ethnology, the latter is no less so to a true understanding of history. The two sciences mutually shed light on one another's path, and though one of them is as yet in its infancy, its wonderful progress in so short a time, and the almost unparalleled attention which it has excited at all hands, are bright omens for the future. It will be obvious that, by _ethnology_, we do not mean _ethnography_, with which it has long been synonymous. Their meaning differs in the same manner, they bear almost the same relation to one another as _geology_ and _geography_. While ethnography contents herself with the mere description and classification of the races of man, ethnology, to borrow the expressive language of the editor of the _London Ethnological Journal_, "investigates the mental and physical differences of mankind, and the organic laws upon which they depend; seeks to deduce from these investigations principles of human guidance, in all the important relations of social and national existence."[18] The importance of this study cannot be better expressed than in the words of a writer in the _North British Review_ for August, 1849: "No one that has not worked much in the element of history, can be aware of the immense importance of clearly keeping in view the differences of race that are discernible among the nations that inhabit different parts of the world.... In speculative history, in questions relating to the past career and the future destinies of nations, _it is only by a firm and efficient handling of this conception of our species, as broken up into so many groups or masses, physiologically different to a certain extent, that any progress can be made, or any available conclusions accurately arrived at_."[19]