is placed in the focus, § 61. the phosphorescence procured on a plate coated with sensitive paint by a molecular torrent skirting along it, Fig. 15, p. 17; the brilliant colors—turquoise blue, emerald, orange, ruby-red—with which grey, colorless objects, and clear, colorless crystals glow on their struck faces when lying separately or piled up in a heap in the course of a molecular torrent, § 55. “electrical evaporation” of negatively electrified liquids and solids, § 59. (_Ro. So. Proc._, June 11, ’91.) the seemingly red-hot glow, but with no heat conducted inwards from the surface, of cool solid silver kept negatively electrified in a vacuum 1/1,000,000 of an atmosphere, and thereby caused to rapidly evaporate, § 40 and 139_a_. This last named result is almost more surprising than the phosphorescent glow excited by molecular impacts on bodies not rendered perceptibly phosphorescent by light, § 55, at centre. Both phenomena will usually be found very telling in respect to the molecular constitution of matter and origination of thermal radiation, whether visible as light or not. In the whole train of Crookes investigations on the radiometer, the viscosity of gases at high exhaustion, and the electro-phenomena of high vacuums, ether seems to have nothing to do except the humble function of showing to our eye something of what the molecules and atoms are doing. The same confession of ignorance must be made with reference to the subject dealt with in the important researches of Schuster and J. J. Thomson on the passage of electricity through gases. Even in Thomson’s beautiful experiments, showing currents produced by circuital electro-magnetic induction in complete poleless circuits, the presence of molecules of residual gas or vapor seems to be _the essential_. It seems certainly true that without the molecules, electricity has no meaning. But in obedience to logic, I must withdraw one expression I have used. We must not imagine the “presence of molecules is _the_ essential.” It is certainly _an_ essential. Ether is certainly also _an_ essential, and certainly has more to do than merely to telegraph to our eyes to tell us what the molecules and atoms are about. If the first step towards understanding the relations between ether and ponderable matter is to be made it seems to me that the most hopeful foundation for it is knowledge derived from experiment on electricity in high vacuum; and if, as I believe is true there is good reason for hoping to see this step made, we owe a debt of gratitude to the able and persevering workers of the last 40 years who have given us the knowledge we have; and we may hope for more and more from some of themselves and from others encouraged by the fruitfulness of their labors to persevere in the work.”