Plate 50.--B, B, B, B, B, planets. Fig. 1, photosphere, or light on every side; Fig. 2, negative currents; Fig. 3, relative enlargement of a planet on the illuminate side; Fig. 4, enlargement illustrative of age of planet; Figs. 5 and 8, variation in vortex, called variation of needles; 1, 1, etherea, or inactive space; 2, 2, 2, 2, place of actinic force. The Panic signs denote the expression in numbers.