320 CONDITION OF THE FLOOE OF THE OCEAN. 



There are plicated regions which are little or not at all elevated, and 

 there are elevated regions which are not plicated." 



Speaking of great regional uplifts, he says further: 



" What the real nature of the uplifting force may be is, to my mind, 

 an entire mystery, but I think we may discern at least one of its attri- 

 butes, and that it is a gradual expansion or diminution of density of 

 the subterranean magmas. * * * We know of no cause which 

 could either add to the mass or diminish the density, yet one of the 

 two must surely have happened. * * * Hence I infer that the 

 the cause which elevates the land involves an expansion of the under- 

 lying magmas, and the cause which depresses it is a shrinkage of the 

 magmas. The nature of the process is at present a complete mystery." 



I shall endeavor to show how the detailed study of marine deposits 

 may help to solve the mystery here referred to by Dutton. 



The surface of the globe has not always been as we now see it. 

 When, in the past, the surface had a temperature of about 400*^ F., 

 what is now the water of the ocean must have existed as water vapor 

 in the atmosphere, which would thereby — as well as because of the 

 presence of other substances — be increased in density and volume. 



Life, as we know it, could not then exist. Again, science foresees a 

 time when low temperatures, like those produced by Professor Dewar 

 at the Roj^al Institution, will prevail over the face of the earth. The 

 hydrosphere and atmosphere will then have disappeared within the 

 rocky crust, or the waters of the ocean will have become solid rock, 

 and over their surface will roll an ocean of liquid air about 40 feet 

 in depth. Life, as we know it, unless it undergoes suitable secular 

 modifications, will be extinct. Somewhere between these two indefi- 

 nite points of time in the evolution of our planet it is our privilege to 

 live, to investigate, and to speculate concerning the antecedent and 

 future condition of things. 



When we regard our globe with the mind's eye, it appears at the 

 present time to be formed of concentric spheres, very like, and still 

 very unlike, the successive coats of an onion. Within is situated the 

 vast nucleus or centrosphere; surrounding this is what may be called 

 the tektosphere,^ a shell of materials in a state bordering on fusion, 

 upon which rests and creeps the lithosphere; then follow hydrosphere 

 and atmosphere, with the included biosphere.^ To the interaction 

 of these six geospheres, through energy derived from internal and 

 external sources, may be referred all the existing superficial phenomena 

 of the planet. 



The vast interior of the planetary mass, although not under direct 

 observation, is known, from the results of the astronomer and physi- 

 cist, to have a mean density of 5.6, or twice that of ordinary surface 

 rock. The substances brought within the reach of observation in vein- 



1 TT/K-ros, molteu. ^ ftioc,. 



