THE HISTORY OF A STAR. 8i 



those farther away will be less metallic. Bit by bit, in the case of 

 the interior bodies, we shall have these permanent gases coming 

 back again, and more carbon will be added to their superficial 

 layers ; those bodies also must condense before the central one. 



If we consider the conditions of the outer condensations, they 

 must be particularly rich in permanent gases. We shall, there- 

 fore, get in the case the outer bodies excessively small density, 

 and probably associated with that only the very sparse presence 

 of these metals which have been alone allowed to penetrate toward 

 the center, because their vapors can condense. 



Our sun must ultimately go through the stage in which its 

 absorption will be due no longer to hydrogen, or to iron, but to 

 carbon, chiefly by virtue of the process which has been referred 

 to ; and eventually, as its radiant energy gets less and less, as it 

 gets cooler and dimmer, the last speck of blood-red sunlight will 

 be put out by an excess of carbon vapors in its atmosphere. 



That is what must have happened to our own earth. It is a 

 very interesting question indeed to attempt to determine at what 

 period of the sun's history a solid crust was formed on the planet 

 on which we dwell. It looks very much as if the consolidation of 

 the earth may have preceded the highest point of temperature of 

 the sun that is to say, that the earth may have reached a condi- 

 tion closely resembling its present one at the time the sun occu- 

 pied the apex of the temperature curve to which reference has 

 been made. 



In any case the high density of the earth, compared with the 

 density of its crust (the enormous quantity of silicon and oxygen 

 and carbon near the crust having an entirely different specific 

 gravity from the specific gravity of the earth taken as a whole), 

 seems to follow as a matter of course from these considerations. 



I trust it will be seen that the hypothesis we have been consid- 

 ering supplies us with an orderly progression of meteoritic dust 

 through heat conditions produced by collisions till finally a cool 

 mass is produced ; that this orderly progression brings about all 

 the known phenomena of the heavens on its way, and simply and 

 sufficiently explains them. But, though much of the mystery is 

 gone, all the majesty is left indeed, to my mind it is vastly in- 

 creased. It seems as if the working out of the meteoritic idea 

 will entirely justify Kant's conviction that the physical side of 

 the science of the universe would in the future reach the same de- 

 gree of perfection to which Newton had in his time brought the 

 mathematical side. Nineteenth Century. 



[Note. In the foregoing remarkable paper the well-known astronomical author and 



authority, Prof. Lockyer, demonstrates, by a process of observation and reasoning which 



carries conviction with it at almost every step, the evolution of all the numberless kinds 



of matter, from the most primary form or substance recognizable by our senses, assisted 



vol. xxxviii. 6 



