﻿572 Dr. S. Tolver Preston on Certain Questions 



by meteoritic bodies known to be scattered everywhere in 

 stellar space (through which our system is moving as a whole 

 at a speed estimated at four * miles per second) ; also in view 

 of the meteoritic theory of cosmical evolution, coupled with 

 the observed powerful magnetic qualities of our globe, — its 

 more central portions may well be constituted of the metal 

 iron. And certainly the fact that gravitation by itself alone 

 would suffice to produce (without the aid of heat) sphericity 

 and the flow even of metals, would appear too interesting a 

 point to neglect f altogether. 



A metallic constitution for the chief bulk of our globe 

 [the metal iron] would be quite consistent with the measured 

 specific gravity of 5*5: this being considerably greater than that 

 of ordinary rocks. The keeping of alternative possibilities in 

 view, so long as they be not inconsistent with recognized 

 facts, may be an aid to progress and eventual demonstration. 



In an address before the British Association at South 

 Africa, chiefly on astronomical science, by Sir George Darwin, 

 where the subject is popularly dealt with, is the following 

 passage, which may be quoted in connexion with the fore- 

 going :— 



" The problems of cosmical evolution are so complicated 

 that it is well to conduct the attack in various ways at the 

 same time. Although the several theories may seem to some 

 extent discordant with one another, yet, as I have already 

 said, we ought not to scruple to carry each to its logical 

 conclusion. We may be confident that in time the false will 

 be eliminated from each theory ; and when the true alone 



* Few probably realize that for the sun (or solar system), with its 

 estimated proper motion of four miles per second, to move a distance equal 

 to that of a Centauri [parallax = 0"'93], would demand but a small 

 fraction of the life-history of the solar system, namely, 161,000 years 

 (only). In the mean life of a system, average stellar distances in our 

 universe would, it appears, be traversed some thousands of times. A 

 diversity of physical conditions at diverse epochs may thus be presented 

 to the speculative view, including possible gradual variation of the 

 " temperature of space." 



t At the Sufi's centre the pressure (according to the calculation of 

 Prof. See) would be that of a mercury manometer projecting beyond the 

 sun's radius, with the quicksilver supposed subject everywhere to the 

 value g for acceleration at the earth's surface. 



"With such pressures as this, may not molecules (now recognized to 

 consist of corpuscles) be, so to speak, "crushed out of shape" to some 

 extent at least in the vicinity of the centre of the sun or of our globe, 

 and so escape as " radioactive material " ? 



Is it likely that pressure without assigned limit can be sustained by 

 minute configurations moving in orbits, without entailing a radical dis- 

 turbance of dynamical equilibrium ? 



