This is not the place to enter on such an enquiry, but so far as can at present be seen, it seems that mankind has progressed not so much by advance within the limits of certain races as by the superposition of more highly organized races over those of an inferior class. Thus we have those stone men of the caves who possessed the world for 100,000 or a million of years, and made no more progress in that period than the animals they were associated with. Even the progress from a chipped to a polished stone implement seems to have been taught them by a foreign bronze-using people. We have then such races as the Egyptian, the Chinese, or the Mexican, who can progress to a certain point, but stop and cannot go beyond; and, lastly, we have the Aryans, the last to appear in the field, but the most energetic, and the only truly progressive race. Our great error in reasoning with regard to the older races seems to be that we insist on applying to them the reasoning and principles which guide us, but which are wholly inapplicable to the less progressive races of mankind. All this will be plainer in the sequel; but in the meanwhile it may safely be asserted that, up to this time, no royal road has been discovered that leads to an explanation of our megalithic antiquities. No one has yet been able so to classify the contents of cognate monuments as to construct a chronometric scale which is applicable for the elucidation of their dates; and no _à priori_ reasoning has been hit upon that is of the smallest use in explaining either their age or their peculiarities. The one path that seems open to us is a careful examination of each individual monument, accompanied by a judicial sifting of all or any traditions that may attach to it, and aided by a comparison with similar monuments in other countries. By this means we have a chance of arriving at a fair proximate degree of certainty; for, though no one monument will tell its own tale directly, a multitude of whispers from a great number may swell into a voice that is clear and distinct and be audible to every one; while no system yet invented, and no _à priori_ reasoning, can lead to anything but deepening the ignorance that now prevails on the subject. This is especially true with regard to the great megalithic circles in this country. With the rarest possible exceptions, no flint and no bronze or iron implements have been found within their precincts. They cannot be older than the invention of flint implements, and iron has been in continuous use since the art of smelting its ores was first discovered. If, therefore, they have no written or traditional history which can be relied upon, their age must for ever remain a mystery. The conviction, however, under which this book is written is that such a history does exist; that, when all the traditions attached to the monuments are sifted and weighed, they amount to such a mass of circumstantial evidence as