IN THE SOLAR SYSTEM. 



83 



and to remain in proximity to each other about eight hours. By this scheme Professor 

 Olmstead undertook to account not only for the phenomenon under consideration, but also 

 for the shooting stars of the 13th November * This hypothesis has been adopted by M. 

 Biot. 



Another hypothesis of American origin, is that of the Rev. George Jones, Chaplain U. 

 S. Navy. This gentleman, during a voyage to Japan, in the frigate Mississippi, had ample 

 opportunities to examine the zodiacal light between the tropics. Observing that the phe- 

 nomenon was visible until midnight, not only in the west, but also in the east, he drew the 

 conclusion that the earth was surrounded by a nebulous ring within the orbit of the moon. 

 He also holds the opinion that the moon, by her light, occasionally produces the zodiacal 

 phenomenon.'!' 



Let us examine critically into the competency of some of these hypotheses to explain 

 the cause of the zodiacal light. 



In this attempt we must be guided in a great measure by the laws of perspective, which, 

 from the antiquity of the arts of designing and painting, are more thoroughly explored 

 and practically understood than those of almost any other science. 



The conjecture most in vogue to explain this phenomenon, is that of a nebulous ring- 

 between the orbits of Venus and Mars. Such a ring must be either equidistant from the 

 sun with the earth's orbit, within,, or beyond it. 



Let us suppose first, that it is equidistant with the earth's orbit, that our planet moves 

 through the heart of the ring, as a string is passed through a circle of beads. 



Our observer shall be stationed upon the equator at sunset, on the 21st March. If he 

 should raise his eyes towards the zenith, and fix them upon a point 23° 28' north of the 

 same he would be looking towards that part of space which the earth had just left. He 

 would therefore, look into the substance of the ring. The reflection of the suns light 

 should cause a visible brightness in that part of the heavens, which should fade towards 

 the horizon; besides which, there should be a prolongation of light extending from the 

 point in question towards the western horizon, decreasing in width, but not in brilliancy, 

 to the latter. The cause of this prolongation of light would be the part of the ring occu- 

 pying the quadrant of the earth's orbit Which had been last passed over. 



As the night passed on, our observer woidd find that the brilliant spot near his zenith 

 was sinking towards the west, and at midnight had set. If at this moment he should turn 

 his eyes to the east, he would discover a similar bright spot rising; he would then be look- 

 ing again into tlve substance of the ring, but towards the opposite point of space, that, in 

 fact, towards which the earth was moving. As this spot rose towards the zenith, he would 



* American Journal of Science and Art, vol. xxix, p. 376. 



t Astronomical Journal, Cambridge, Mass., No. 84, May 26, 1855. 



