"Arago was of the opinion that each observer saw his own aurora somewhat as each observer of a rainbow sees the luminous arc differently placed."
The Great Sun Battery.
10. ([Page 44.]) If with a percussion cap and a tear we may develop sufficient power to deflect a magnetic needle 3,000 miles distant, what power may not be expected of the sun, 1,250,000 times larger than the earth; the sun exercising a force of the same character?
Gravity.
11. ([Page 50.]) "Prof. Mossotti has recently shown, by a very able analysis, that there are strong grounds for believing that not only the molecular forces which unite the particles of material bodies depend on the electric fluid, but that even gravitation itself, which binds world to world, and sun to sun, can no longer be regarded as an ultimate principle, but the residual portion of a far more powerful force, generated by that energetic agent which pervades creation."—Faraday.
"If gravitation is made to mean something allied to magnetism, some poorly explained phenomena become easily understood. But what are the circumstances affording proof of the identity of these forces? First, gravitation acts upon all kinds of matter; Faraday proved the same of magnetism. Second, gravitation is attractive; so is magnetism. Third, gravitation is proportionate to the mass; the force of magnets also depends upon the mass. Fourth, gravitation acts in an inverse ratio to the square of the distance; so does magnetism. Fifth, gravitation does not manifest polarity; magnetism is known not to do so. Sixth, gravitation acts independently of bodies affording a resistance to light and heat; so does magnetism."—Cartwell.
Faraday's biographer says:—"He is oppressed with the magnitude and importance of his subject, yet is stimulated by the fact that the discovery which he aims for (the relationship between gravity and electricity) would have a bearing in importance far beyond all conception in elucidating not only the facts connected with these subjects, but also others of a high importance. There being scarcely a limit to the subjects which would be illuminated by it."
"Gravity, surely this force must be capable of an experimental relation to electricity and magnetism and the other forces, so as to bind it up with them in reciprocal action and equivalent effect."—Faraday.
Kepler regarded gravity and heat "as being probably derived from one single principle."