So, then, all you have to do, gentlemen, is to forbid the light to blacken iodine, or order it to blacken lime, and condemn the photographer to develop his negative in full light. Ask Electricity why it will pass instantaneously from one end to the other of an iron wire a thousand miles long and why it refuses to traverse a thread of glass half an inch long. Beg the night-blooming flowers to expand in the day, or those that only bloom in the light not to close at dusk. Give me the explanation of the respiration of plants, diurnal and nocturnal, and of the production of chlorophyll and how plants develop a green color in the light; why they breathe in oxygen and exhale carbonic acid gas during the night, and reverse the process during the day. Change the equivalents of simple substances in chemistry, and order combinations to be produced. Forbid azotic acid to boil at the freezing temperature, and command water to boil at zero. You have only to ask these accommodations and nature will obey you, gentlemen, depend upon it. A good many phenomena of nature only occur in obscurity. The germs of plants, animals, man, in forming a new being, work their miracle only in the dark. Here, in a flask, is a mixture of hydrogen and chlorine in equal volumes. If you wish to preserve the mixture, you must keep the flask in the dark, whether you want to or not. Such is the law. As long as it remains in the dark, it will retain its properties. But suppose you take a schoolboy notion to expose the thing to the action of light. Instantly a violent explosion is heard; the hydrogen and the chlorine disappear, and you find in the flask a new substance,--chloridic acid. There is no use in your finding fault: darkness respects the two substances, while light explodes them. If we should hear a malignant sceptic of some clique or other say, "I will only believe in jack-o'-lanterns when I see them in the light of day," what should we think of his sanity? About what we should think if he should add that the stars are not certainties, since they are only seen at night. In all the observations and experiments of physics there are conditions to be observed. In those of which we are speaking a too strong light seems to imperil the success of the experiment. But it goes without saying that precautions against deception ought to increase in direct ratio with the decrease of visibility and other means of verification. Let us return to our experiments. 6. Taps are heard in the table, or it moves, rises, falls back, raps with its leg. A kind of interior movement is produced in the wood, violent enough, sometimes, to break it. The round table I made use of (with others) in my home was dislocated and repaired more than once, and it was by no means the pressure of the hands upon it that could have caused the dislocations. No, there is something more than that in it: there is in the actions of the table the intervention of mind, of which I have already spoken.