"I have been told," I answered, "that vapor of water causes this obscuration, or absorption, of light." "Vapor of water, unless in strata of different densities, is absolutely transparent, and presents no obstacle to the passage of light," he said. "When vapor obstructs light it is owing to impurities contained in it, to currents of varying densities, or wave motions, or to a mechanical mixture of condensed water and air, whereby multitudes of tiny globular water surfaces are produced. Pure vapor of water, free from motion, is passive to the sunlight." "I can scarcely believe that a substance such as you describe, or that any constituent of the air, can have escaped the perception of the chemist," I replied. In, as I thought, a facetious manner he repeated after me the word "chemist," and continued: "Have chemists detected the ether of Aristotle, that you have mentioned, and I have defined, which scientists nevertheless accept pervades all space and every description of matter, and that I have told you is really matter itself changed into ultra atomic motion? Have chemists explained why one object is transparent, and another of equal weight and solidity is opaque? Have chemists told you why vermillion is red and indigo is blue (the statement that they respectively reflect these rays of light is not an explanation of the cause for such action)? Have chemists told you why the prism disarranges or distorts sunlight to produce the abnormal hues that men assume compose elementary rays of light? Have chemists explained anything concerning the why or wherefore of the attributes of matter, or force, or even proven that the so-called primary forms of matter, or elements, are not compounds? Upon the contrary, does not the evolution that results in the recorded discoveries of the chemist foretell, or at least indicate, the possible future of the art, and promise that surrounding mysteries are yet to be developed and expanded into open truths, thus elaborating hidden forces; and that other forms of matter and unseen force expressions, are destined to spring into existence as the sciences progress? The chemist of to-day is groping in darkness; he is a novice as compared with the elaborated chemist of the near future; the imperfectly seen of the present, the silent and unsuspected, will become distinctly visible in a time that is to come, and a brightening of the intellect by these successively upward steps, up stairs of science, will, if science serves herself best, broaden the mind and give power to the imagination, resulting finally in--" He hesitated. "Go on," I said. "The passage of mortal man, with the faculties of man intact, into communion with the spirit world." CHAPTER XXXIII. "A STUDY OF SCIENCE IS A STUDY OF GOD."--COMMUNING WITH ANGELS. "This is incredible," I exclaimed.