﻿574 Dr. S. Tolver Preston on Certain Questions 



of the breadth of the zones — become eventual planets, is not 

 entered upon. But the significance of the zones "in which 

 stable orbits are possible'''' appears to be that only under 

 this condition could meteoritic bodies coming from space 

 accumulate [be virtually " selected"], constituting presumably 

 material rings of discrete fragments of matter, somewhat 

 reminding of the rings of Saturn *. 



There is the difficulty, however, that a ring of material 

 can only concentrate (aggregate) about its centre of gravity, 

 which would imply its ultimately falling into the sun or 

 central body. 



But it might possibly be proposed that the mere fortuitous 

 entry of meteorites (possessing a suitable " direction and 

 speed ") into these zones, would, by the laws of probability, 

 condition [round a given zone] an irregular distribution of 

 material, rather than the reverse ; thus virtually constituting 

 an ill-balanced or broken ring ; which might then concentrate 

 into a planet j. And we have seen that, without the necessity 

 for a preceding nebulous state, gravitation by itself can pro- 

 duce the compacted flow of even solid substance into a natural 

 globular (or rather oblate) form ; while internal heat for the 

 inhabitability of a planet is of no use whatever. 



Here seems a fit opportunity for inviting attention to the 

 importance of according due weight in cosmology to Hutton 

 and LyelFs principle or (rather) factor of slow progressive 

 changes, under a proper extension of time, coupled with 

 natural causes at present observed to be in action, — which is 



acknowledged to have contributed so much to enlightenment 



© © 



in the allied science of geology. This slow natural process 



* In reference to Saturn, Sir George Darwin remarks : — " The 

 astonishing discovery has just been made by William Pickering of a 

 ninth retrograde satellite of Saturn, while the rotations of the eight 

 other satellites, of the ring, and of the planet itself, are direct." (Address, 

 p. 440, in l Nature'). 



But in that same Journal (only 27th of April previously — same year), 

 is a letter by Prof. William J. Pickering (p. 608), where he expresses 

 rather the reverse of surprise at this retrograde motion of the satellite 

 discovered by him, and proposes to harmonize its motion with a funda- 

 mental property of gyrostatic motion, which, since his letter bears the 

 title — " A little known Property of the Gyroscope," Prof. Pickering would 

 seem to consider has escaped an adequate appreciation. 



+ It may be just worth a passing notice that in a so-called "meteoritic 

 plenum," the components of any " double " (forming after the manner 

 described in the moon's evolution) would differentiate in mass, after 

 separation or severance, on account of more meteorites falling continually 

 into the greater or central body. Thus it might seem that the mass 

 (say of a " large planet ") which was judged too small relatively to the 

 primary for this particular evolutionary process to be applicable, might 

 have been more equal to the primary at the very remote epoch when 

 this " double " originated (or could have originated). 



