On this important subject we have another observation to make, which refers more properly to an incidental circumstance in primitive history; for our great business is with the moral and intellectual progress of man. But even in respect to this more important object, the circumstance which we allude to should not be passed over in silence, as it tends to exemplify, illustrate and confirm the principle we have already had occasion to enforce; namely that we ought not to estimate by the narrow standard of present analogies and vulgar probabilities, all those facts in primitive nature and in primitive history which strike us as so strange, mysterious, and marvellous; provided they be really attested by ancient monuments and ancient tradition. We should ever bear in mind what a mighty wall of separation--what an impassable abyss--divides us from that remote world both of nature and of man. I refer to the unanimous testimony of ancient tradition respecting the gigantic forms of the first men, and their corresponding longevity, far exceeding, as it did, the present ordinary standard of the duration of human life. With respect to the latter circumstance, indeed, there are so very many causes contributing to shorten considerably the length of human life, that we have completely lost every criterion by which to estimate its original duration; and it would be no slight problem for a profound physiological science to discover and explain from a deeper investigation of the internal constitution of the earth, or of astronomical influences, which are often susceptible of very minute applications the primary cause of human longevity. By a simpler course of life and diet than the very artificial, unnatural and over-refined modes we follow, there are even at the present day numerous examples of a longevity far beyond the ordinary duration of human life. In India it is by no means uncommon to meet with men, especially in the Brahminical caste, more than a hundred years of age, and in the enjoyment of a robust, and even generative vigour of constitution. In the labouring class in Russia, whose mode of living is so simple, there are examples of men living to more than a hundred, a hundred and twenty, and even a hundred and fifty years of age; and although these instances form but rare exceptions, they are less uncommon there than in other European countries. There are even remarkable cases of old men, who after the entire loss of their teeth, have gained a complete new set as if their constitution had received a new sap of life, and a principle of second growth. What, in the present physical degeneracy of mankind, forms but a rare exception, may originally have been the ordinary measure of the duration of human life, or at least may afford us some trace and indication of such a measure; more especially as other branches of natural science offer correspondent analogies. On the other side of that great wall of separation which divides us from the primitive ages--in