text:  The following passage is the most explicit we can find on the subject of the connexion between the _physique_ and _morale_ and at the same time will serve to introduce the three varieties of skull which the author deems principally worth notice:-- "If any method of subdividing the human family into groups is likely to be of any particular advantage in elucidating the natural history of the species it must be one founded on some relation between the physical characteristics of different tribes and the leading circumstances of their external condition