THE HAMILTON ASSOCIATION. _ 65 



heavier or denser ones. They would gravitate towards Venus, which 

 hes inside our orbit, and be the first to fall on it, whilst the denser 

 fragments, metalloids and metals, would be the last. 



Dr. Brewster favors the theory of meteoroids being fragments 

 of a large planet similarly as the asteroids, the previous existence of 

 which was long ago suggested by the vast chasm between Mars and 

 Jupiter, where only asteroids have as yet been observed. Dr. Gi- 

 bers, the discoverer of three of the known asteroids, held the same 

 idea, and that the lesser fragments, coming within the attractive 

 power of a planet would fall towards it^ and when entering its atmos- 

 phere would go through all the conditions referred to, fusion, lumin- 

 osity, etc. Sir John Herschel, however, differs from this theory. 

 The diameter of Jupiter, the largest known body in our planetary 

 system, is 80,000 miles, whilst that of Clio, one of the smallest, is 

 only 16 miles, Chladin, a philosopher, at the end of the last cen- 

 tury, thought that bodies might exist as much smaller in comparison 

 as Clio to Jupiter, having only 16 feet diameter, and in the same 

 ratio we come down to i-25th of an inch, mere cosmic dust. To 

 this cosmic dust has been attributed that pecuhar fleecy brightness 

 known as the Zodiacal light. Any observer of the western sky at 

 this season of the year (the early spring) for about an hour after 

 sunset, may see a soft, faint cone-shaped glow hght extending about 

 40 degrees, following nearly the sun's path in the heavens. Near 

 the equator, where the elliptic rises high above the horizon, it can 

 be seen nearly all the year round, and in a very clear atmosphere in 

 the tropics has been traced all the way across the heavens from east 

 to west, forming a complete ring. The theory that now prevails is 

 that the light from the sun when below our horizon reflected on the 

 cosmical atoms of floating star-dust and meteoroids, is the cause of 

 the soft celestial glow that now lingers evening after evening in our 

 western sky. An illustration of this is offered by a ray of light 

 which finds its way into a darkened room through a small orifice, 

 revealing as motes dancing in the sunbeam the particles of dust 

 floating in the air of the room, but visible only where the entering 

 ray of light falls athwart them. 



In this connection, the recent deep sea soundings of the 

 "Challenger" have brought to light a curious fact. Sir Wyville 

 Thomson found that beds of sediment were being slowly formed on 

 the deepest ocean floors, but so slow was the rate of deposition 



