variability of the star Mira 178 Fig. 41. Lineal nebula in Sobieski's Crown which has been affected by currents in the ocean of space 189 Figs. 42 to 45. Four stages in the phenomena of a new or temporary star, a "star in flames;" reversal of the hydrogen lines in its spectrum 196 Figs. 46 and 47. Illustration of repulsion of the tail of a comet by the similarly electrified solar electrosphere; comparison with similar repulsion in a vacuum-chamber experiment 211 Figs. 48 and 49. The electroscope, and mutual electrical repulsion in a bundle of dry straws 225 Fig. 50. Experiment with a candle and currents of air from between two disks, illustrating the radial semi-rotation of a comet's tail during perihelion 230 Figs. 51 to 54. Four non-systemic gaseous nebulæ: Fig. 1, crab nebula; Fig. 2, dumb-bell nebula; Fig. 3, lineal nebula in Sobieski's Crown; Fig. 4, Catherine-wheel nebula. The latter illustrates the formation of a planetary nebula with a hollow center, or else dispersion into the elements of space again 263 Fig. 55. Great spiral nebula in Canes Venatici and a small adjacent nebula affected thereby 273 Figs. 56 to 59. Four gaseous nebulæ in process of development into solar systems: Fig. 1, divergent spiral; Fig. 2, later stage of a similar spiral; Fig. 3, subsequent stage of rupture of the nearly circular convolutions of a similar nebula; Fig. 4, the same stage in the development of a solar system with a double sun 279 Fig. 60. Nucleated planetary nebula, showing its external ring split and held apart, in part of its circumference, by electrical repulsion 288 Fig. 61. Divergent spiral nebula on cover of book. INTRODUCTION.