In like manner the North American Indians have been very little influenced by the residence of some millions of proselytizing Europeans among them for 200 years, and while this is so, it seems most groundless to argue because a few Phœnician traders may have visited this island to purchase tin, that, therefore, they introduced their manners and customs among its inhabitants; or because a traveller like Pytheas may have visited the Cimbrian Chersonese, or even penetrated nearly to the Arctic Circle, that his visit had, or could have, any influence on the civilization of these countries.[54] Civilization, as far as we can see, was only advanced in northern and western Europe by the extermination of the ruder races. Had this rude but effective method not been resorted to, we should probably have a stone-using people among us at the present day. We may not know much of what happened in northern Europe before the time of the Romans, but we feel tolerably safe in asserting that none of the civilized nations around the Mediterranean basin ever colonized and settled sufficiently long in northern Europe to influence perceptibly the manners or usages of the natives. What progress was made was effected by migrations among themselves, the more civilized tribes taking the place of those less advanced, and bringing their higher civilization with them. If these views are at all correct, it seems hopeless by any empirical theories founded on what we believe ought to have happened or on any analogies drawn from what occurred in other countries to arrive at satisfactory conclusions on the subject. It is at best reasoning from the unknown towards what we fancy may be found out. A much more satisfactory process would be to reason from the known backwards so far as we have a sure footing, and we may feel certain that by degrees as our knowledge advances we shall get further and further forward in the true track, and may eventually be able to attach at least approximative dates to all our monuments. From this point of view, what concerns us most, in the first instance at least, is to know how late, rather than how early, our ancestors buried in tumuli. We have, for instance, certainly, the Bartlow Hills, just alluded to, which are sepulchres of the Roman period, probably of Hadrian's time; and we have in Denmark the tumuli in which King Gorm and his English wife, Queen Thyra Danebode, were buried in A.D. 950. We probably also may be able to fill in a few others between these two dates, and add some after even the last. Thus, therefore, we have a firm basis from which to start, and working backwards from it may clear up some difficulties that now appear insuperable. DOLMENS.