The overlapping of the sciences is made the subject of much rhetorical writing now-a-days, and its appreciation is one of the most prominent signs of the modern development of the doctrine of Continuity which has been so fruitful in the Philosophy of Discovery. The boundary-line which once separated the geologist and ethnologist has in consequence of this development entirely disappeared, and every one now admits as a postulate that between the two sciences there is a stretch of neutral ground belonging to neither exclusively, and where the students of each must of necessity reap if their harvest is to be complete. Not only so, but it is beginning to be seen that the methods and the directions of the arguments in each science being more or less different—the one partaking much more of the historical, and the other of the experimental method—that it is well that where they overlap the results of each should be closely compared, and thus not only secure a double modicum of certitude, but also suggest fresh veins of untried material where we may put in our mattock with renewed hope of solving some apparently hopeless problems.