When we remember that the Great Pyramid covers 13½ acres of ground, that it is truly square and on a truly horizontal base, that each side is accurately directed to a point of the compass, that the angle of its slope is such that the area of each of the four triangular faces is equal to that of a square whose sides are equal to the height of the pyramid; and, further, that the slope of the long descending tunnel is precisely such as to point accurately to the pole star of the epoch at the lowest part of its circuit round the true pole; and, lastly, that all this could only be done, as accurately as it has been done, by the system of subterranean tunnels and galleries that actually exists, while almost all the details of their construction are shown to be adapted for astronomical observations of the nature required, the conclusion becomes irresistible that they were designed and used for such observations, and that by no other means could the same amount of accuracy have been attained. I have given a rather full account of what the Pyramid builders really did, because it forms a very important part of the argument I am developing as to the stationary condition of the human intellect during the historical period. The great majority of educated persons hold the opinion that our wonderful discoveries and inventions in every department of art and science prove that we are really more intellectual and wiser than the men of past ages—that our mental faculties have increased in power. But this idea is totally unfounded. We are the inheritors of the accumulated knowledge of all the ages; and it is quite possible and even probable, that the earliest steps taken in the accumulation of this vast mental treasury required even more thought and a higher intellectual power than any of those taken in our own era. We can perhaps best understand this by supposing any one of our great men of science to have been born and educated in one of the earliest of the civilisations. If Newton had been born in Egypt in the era of the Pyramid builders, when there were no such sciences as mathematics, perhaps even no decimal notation which makes arithmetic so easy to us, he could probably have done nothing more than they have actually done. In building up the sciences each of the early steps was the work of a genius. But now that there has been nearly a hundred centuries of discovery and specialisation by thousands or even millions of workers, that by means of writing and of the printing press every discovery is quickly made known, and that ever larger and larger numbers devote their lives to study, the rate of progress becomes quicker and quicker, till the total result is amazingly great. But that does not prove any superiority of the later over the earlier discoveries. There is, therefore, no proof of continuously increasing intellectual power. But we have now evidence of another kind, which adds to the force of this argument.