carbon increases with the temperature, thus agreeing with the action of liquids." Page 133, "To determine the resistance in liquids, the above methods cannot be employed, liquids being decomposed by the electrical current." Referring to the voltaic arc and the spark of the induction apparatus (page 200), it is said, "Dry air under great pressure offers a high resistance, but a perfect vacuum is a perfect insulator, and between these extremes there are degrees of rarification which admit of a flow of electricity." In general, it is said that electrical decomposition requires that the electrolyte be in liquid form, but this is not universally true, and throughout interplanetary space may not be true at all. In Ferguson's work on Electricity, it is stated that, "The passage of electricity through compound gases in a state of great rarity, as in the so-called vacuum tubes, frequently separates them up into their constituents." So, also, the opinion that electricity cannot be readily conducted through dry gases is refuted by the play of the auroral streamers. The distance from the surface of the earth of these electrical waves and the auroral arch is variously estimated at from seventy to two hundred and sixty-five miles, and in one instance "at a height of from four thousand to six thousand miles;" see article in Appleton's Cyclopædia. Certainly there could be no sensible moisture at the temperatures there prevalent, and especially at night and during the fall and winter months when these displays are very frequent. Whether the currents be due to induction, as between neighboring bodies one of which is electrified, or from direct emission, as in brush discharges, there must obviously be some medium of contact and continuity for the free transference of electrical energy through space. Regarding the rationale of electrolysis ("Electricity in the Service of Man"), after discussing certain other theories, the authors say, "Clausius, too, assumes an electrified condition of the molecules of each electrode, but he neither attributes to the galvanic current the force of direction nor power of decomposing. He points out that both the molecules of fluids and also their atoms are in continual motion. The atoms in molecules of fluids are held together but by a moderate force, and the molecules themselves constantly undergo changes both of synthesis and analysis. The galvanic current merely effects a regulated motion of the atoms; the positive ions are attracted by the negative electrode, and the negative ions by the positive electrode, and by this means are separated out from the liquid." Page 91, "The upper layers of air are more or less electrified, so as to have a potential differing from that of the earth, but how their electrical condition has been produced is not at present known. Condensation of water-vapor is supposed to produce electricity. Close to the earth the air has little or no electricity; the farther from the earth