In addition to what has been already advanced on this subject of a comet's light, we may appeal to the well-known fact that the visibility of a comet is not reciprocally as the squares of the distances from the earth and sun as it ought to be, if shining by reflected light. In Mr. Hind's late work on comets, the fact is stated that "Dr. Olbers found that the comet of 1780 attained its greatest brightness on the 8th of November, thirteen days subsequent to its discovery, whereas according to the law of reflected light, it should have become gradually fainter from the day of its discovery; and supposing the comet self-luminous, the intensity of light should have increased each day until November 26th; yet in the interval between the 8th and 26th of that month, it grew rapidly less." Now this theory teaches, that a comet is neither self-luminous nor dependent on the sun, but on its distance from the axis of the vortex, and a certain amount of elapsed time from the perihelion, varying somewhat in each particular case. This fact is therefore a very strong argument in favor of our theory. Amidst the many anomalous peculiarities of comets, it has been noticed that a short tail is sometimes seen at right angles to the principal tail, and in a few cases pointing directly towards the sun. Much of this may be owing to perspective, but granting the reality of the fact, it is still explicable on the same general principles. In speaking of the modifying causes which influence the weather, we mentioned the effect due to the position of the sun with respect to the axis of the vortex. This will be found to have a sensible effect on the action of the radial stream. The natural direction of a comet's electric stream is _towards_ the axis of the vortex, and in the central plane of the vortex it will be also towards the sun. But this stream is met by the stronger radial stream from the axis, and as Mr. Hind describes it, "is driven _backward_ in two streams passing on either side of the head, and ultimately blending into one to form the tail." Now, if the body of the sun be situated between the comet and the axis of the vortex, it will shield the comet from the action of the radial stream, and thus a tail may really point towards the sun.