Hypothesis of an electric or magnetic action in the formation of tails–Eepulsive action of the sun upon the cometary matter, and of the nucleus upon the nebulosity –Views of Sir John Herschel and-M. Liais–Theory of Bessel–Oscillations of luminous sectors–Magnetic polar force.

Whether the cause which determines the production of cometary tails and their development, at once so immense and so rapid, be a force sui generis, or only an apparent force, it is none the less true that it has all the features of a repulsive action or force. Heat, the impulsion of the solar rays, gravitation, have all been variously combined in order to furnish the desired explanation; it evidently remained to try the intervention of the electric and magnetic forces.

From this point of view Olbers, Herschel, and Bessel have in turn applied themselves to the problem. We will give a brief analysis of the opinions held by these illustrious astronomers.

The comet of 1811 first drew the attention of Olbers to the subject. ‘ This astronomer, ’ says M. Roche, ‘ attributes to the proximity of the comet and the sun a development of electricity in both these bodies; hence arises a repulsive action of the sun and another repulsive action of the comet upon the nebulosity which surrounds it. ’