454 Sir J, Oonroy on the Light reflected 



Jupiter), but also an accordant influence of our own planet, 



which is the central orb and the largest planet in the belt 

 which is bounded by the secular perihelion of Mercury and the 

 secular aphelion of Mars. 



Herschel's modified presentation of the nebular hypothesis, 

 and Gummere's criterion, furnish the needful grounds for a 

 satisfactory explanation of such remarkable velocities as that 

 of the inner moon of Mars. They also seem to require that 

 secondary orbs, when they revolve in less time than is required 

 for the rotation of their primaries, should be denser than the 

 primaries. There is therefore good reason for the further pre- 

 diction that, whenever the density of Phobos is ascertained, it 

 will be found to be greater than that of the planet itself. If 

 Mars has any other moons which have an orbital period of less 

 than twenty-four hours, they should also be of like superior 

 density. In these harmonies, as well as in many others, the 

 pointing to the primeval organizing agency of light is inter- 

 esting and suggestive. At the theoretical period, of each of 

 the harmonic divisions, and at all other stages of nebular con- 

 densation, the rhythmical rotation of our day-star has been 

 repeating its unvarying confirmation of the old, old record. 

 In the dim and distant past, in the living present, and through 

 all coming time, from the great " Beginning," until the cul- 

 mination of prophecy when "the elements shall melt with 

 fervent heat," nothing but divine intervention has disturbed, 

 or can disturb, the equality between the accumulated action 

 of solar gravity for a half-rotation and the velocity of light. 

 The harmonic hypothesis forecasts the same requirement at 

 the surface of the central orb in every stellar system; so that 

 the closing refrain in the hymn of each of the morning stars 

 is, was, and ever shall be: — 



" And God said, Let there be light; and there was light." 



LVIII. On the Light reflected by Potassium Permanganate. 

 By Sir John Conroy, Bart., M.A.* 



THE light reflected from the surface of potassium perman- 

 ganate w r as originally examined by Haidinger, who an- 

 nounced {Sitzungsbericlde der kaiserlichen Akademie der Wis- 

 senschaften, Band viii. 1852, p. 133), that when the light 

 reflected from the surface of the crystals and of the substance 

 rubbed on a plate of glass was examined with a dichroiscopic 

 lens, the portion polarized in the plane of incidence w T as light 

 yellow at low angles, and became white as the angle increased, 

 whilst the portion polarized perpendicularly w T as light yellow, 

 and became green and blue as the angle increased. 

 * Communicated by the Physical Society. 



