the bold attempts at solving the problem of the origin and nature of the world, wherein their speculations, often erroneous, nevertheless left a residuum of thoughts that were the seeds of all our higher philosophy. If Thales laid it down that in all the varieties of plant and animal life there was a common element which was their real or original substance, Anaximander thought that caloric (or the igneous principle) was necessary to develop the original material. His book is lost, and his views not clear to us, but we know that his geological observations told him that our world had once been covered with water, from which land had emerged. He was moreover the first to maintain that nothing was eternal except the primeval substance of things. The cloud-capped towers, the gorgeous palaces, The solemn temples, the great globe itself, Yea, all which it inherit, shall dissolve, And, like the baseless fabric of this vision, Leave not a rack behind. We are such stuff As dreams are made on; and our little life Is rounded with a sleep. In the largest sense, even applying it to the gods of the Greek Pantheon, did he assert this colossal doctrine. Anaximenes went further, and, assuming that the particles of ether are the most subtle in the universe, he set up the principle of rarification and condensation of matter, asserting that this was the one great cause of the differences in the bodies we perceive. This then was the first expression of the doctrine of the Atomists, which has lasted to the present day. It is a common piece of arrogance among experimentalists to say that these wonderful anticipations of modern science were mere gropings in the dark, supported not by experiment, but by what we should call superficial observations. The wonder is all the greater that these men should in their theories have gone to the root of the matter, and thought out the metaphysical possibilities of the composition of the world. Abstract thinking--theory--is after all the true basis of every great discovery. In complete disregard of the theological cosmogony derived from the old poets, they openly inaugurated the birth of a natural science engendered by pure and high thinking.