text:  The following passage in which the object of the work is enounced by the author is wanting in precision and perspicuity:-- "That great differences in external conditions by the double influence of their physical and moral agency should have effected during a long series of ages remarkable changes in the tribes of human beings subjected to their operation--changes which have rendered these several tribes fitted in a peculiar manner for their respective abodes--is by no means an improbable conjecture; and it becomes something more than a conjecture when we extend our view to the diversified breeds of those animals which men have domesticated and have transferred with themselves from one climate to another