No one can fully appreciate the great value of this work to all students of ethnology until they realize the historical importance of an accurate classification of the characteristic differences which divide the social strata known as the castes living in a country occupying the geographical position of Bengal. Bengal is practically the country of the Deltas of the Ganges and Brahmaputra, and of the Western rivers, which rise in the Vindhyan range, called by Hindu geographers the Sukti mountains, and flow down thence to the Ganges and the Bay of Bengal. It has always been one of the great highways by which Southern tribes moved northward and Northern tribes southward, and was, owing to its geographical advantages and its fertile soil, civilized and settled before the advent of the Aryan conquerors to North-western India. It is for this reason that we find in Bengal the undisturbed remains and the still living and almost unchanged representatives of some of the principal races who are described by the poets of the Rigveda under the general name of Dasyus, a name which, as Zimmer shows, merely means the people of the country or “desh.” It was from the union of the people of Bengal called the Maghadas or Mughs with the Northern Kushikas or sons of Kush the tortoise that the first great Indian Empire arose, which was formed by the two races ruled by the king called in the Mahābhārata Jarasandha.