may be dismissed from apprehension. It will be seen that all the enormous difficulties in the phenomena of comets find an explanation in the operation of the same universal laws which we have endeavored to apply to the other sidereal bodies. In conclusion, we may cite the following from Dr. Huggins: "Broadly, the different applications of principles of electricity which have been suggested group themselves about the common idea that great electrical disturbances are set up by the sun's action in connection with the vaporization of some of the matter of the nucleus, and that the tail is probably matter carried away, possibly in connection with electric discharges, under an electrical influence of repulsion exerted by the sun. This view necessitates the supposition that the sun is strongly electrified, either negatively or positively, and, further, that in the processes taking place in the comet, either of vaporization or of some other kind, the matter thrown out by the nucleus has become strongly electrified in the same way as the sun,--that is, negatively if the sun's electricity is negative, or positively if the sun's is positive. The enormous disturbances which the spectroscope shows to be always at work in the sun must be accompanied by electrical changes of equal magnitude, but we know nothing as to how far these are all, or the great majority of them, in one direction, so as to cause the sun to maintain permanently a high electrical state, whether positive or negative." The above speculations will have thus become demonstrated facts (though not in the mode suggested by the above writer) as soon as we clearly understand that, instead of the sun's "enormous disturbances" producing "electrical changes of equal magnitude," it is the electrical changes of equal magnitude which themselves cause the sun's disturbances, and that the sun's negative electrical polarity is permanently fixed by the opposite and positive polarity of the planetary electrospheres, and that all these various phenomena are but the normal expression of a single universal law, and are all due to the constant interaction of planetary, solar, and cometic electrospheres, in accordance with the well-established principles of electrical science. If, however, we consider, as is generally believed to be the case, the sun itself to be the sole prime source of its visible energy, nothing but difficulty and vague speculation can be looked for on every hand; but by relegating the solar orb to its proper place, and taking as the starting-point the true source of all energy,--to wit, the hidden forces embodied in the vapors or gases of interstellar space,--the whole process and mode of action will logically follow, and obscurity and difficulty together disappear. This principle, properly understood, is a master-key which will unlock every problem and interpret every enigma which the realms of interstellar space can present. CHAPTER X.