294 FROM NEBULA TO NEBULA 



of supposing that the strength of such solid materials can protect 

 its substance from compression and its effects. We must extend 

 our conceptions beyond what is familiar to us. We know that 

 any ordinary mass of some strong, heavy solid as iron, copper, 

 or gold is not affected by its own weight so as to change in struc- 

 ture to an appreciable extent. The substance of a mass of iron 

 forty or fifty feet high would be the same in structure at the 

 bottom as at the top of the mass; for the strength of the metal 

 would resist any change which the weight of the mass would 

 (otherwise) tend to produce. But if there were a cubical moun- 

 tain of iron twenty miles high, the lower part would be absolutely 

 plastic under the pressure to which it would be subjected. It 

 would behave in all respects as a fluid, inasmuch that if (for con- 

 venience of illustration) we suppose it enclosed within walls 

 made of some imaginary (and impossible) substance which would 

 yield to no pressure, then, if a portion of the wall were removed 

 near the base of the iron mountain, the iron would flow out like 

 water from a hole near the bottom of a cask. The iron would 

 continue to run out in this way, until the mass was reduced sev- 

 eral miles in height. In Jupiter's case a mountain of iron of 

 much less height would be similarly plastic in its lowest parts, 

 simply because of the much greater attractive power of Jupiter's 

 mass. Thus we see that the conception of a hollow interior, or of 

 any hollow space throughout the planet's globe, is altogether in- 

 consistent with what is known of the constitution of even the 

 strongest materials. * * * The effect of pressure in rendering iron 

 and other metals plastic has been experimentally determined. 

 Cast steel has been made to flow almost like water under pressure. 



You may perhaps wonder whether Mr. Proctor, who 

 penned these statements a half century ago, may not have 

 been premature in the making of them, and that later re- 

 searches (during the greatest investigating age of all 

 time) may have contradicted him. No, lie was not mis- 

 taken, nor does contemporary science throw the slight- 

 est cloud of doubt upon either the facts or the inferences 

 as he gives them. Just as Jupiter was then he still is, 

 and such he has been, according to present scientific opin- 

 ion, for as long, or even longer, than the age of the earth 

 say a thousand million of years. Why is he still so 

 hot after a million times as long as (according to the 

 orthodoxical Newcomb), had he been an "ordinary" 

 body, should have been sufficient to cool him down from a 

 solar temperature to a condition such as the moon is in 

 to-day? Jupiter is more than five times as far from the 



