THE GEOSPHERES 445 



and, to some extent, in the uplifting of mountains; it is indi- 

 cated further, in still more interesting though obscure fashion, 

 by the apparent reduction of loose-textured solids to the denser 

 transolid condition in provinces subject to loading through dep- 

 osition of exceptional volumes of sediment — e. g., the Gulf of 

 Mexico, the world's most notable province of loading, whose 

 configuration suggests a hypogean " slump " which may be im- 

 itated experimentally by pouring a few drops of heavier and 

 cooler liquid into a viscid liquid at the critical (or boiling) 

 point; but this most interesting relation may also be passed 

 over for the present with the simple suggestion — made by many 

 phenomena — that the solid litliosphere and transolid centro- 

 sphere appear to be interconvertible at a critical point of tem- 

 perature and pressure, much as the atmosphere and hydrosphere 

 may be considered interconvertible in state and in substance on 

 passing a critical point conditioned by the same factors, and 

 that the hypothesis of interconvertibility explains some of the 

 most puzzling facts in geology. 



There are other interrelations between the geospheres, inter- 

 relations innumerable; time will not permit me to mention a 

 tithe or even a hundredth part of them ; yet there is one more 

 relation which appeals strongly to those geographers who, like 

 myself, always see the lands and the waters from the human 

 standpoint, and I beg your indulgence for the three minutes re- 

 quired to set it forth briefly. My predecessor, Dr Redway, has 

 admirably defined for you the natural provinces of America, and 

 shown you that the features of the land, formed during the ages 

 by the work of running waters, shape the character of our peo- 

 ple. I trust he will permit me to add a word to his theme, as 

 well as to that of the thinker for whom I am speaking : In what 

 we call the western hemisphere the land and the waters are so 

 related as to form a broad continent, the North American con- 

 tinent, mainly in the North Temperate zone ; during the ages 

 the centrosphere has heaved and sunk according to its wont, 

 and has interacted with the atmosphere and hydrosphere in 

 such manner as to produce a litliosphere of far-reaching forma- 

 tions, crumpled here into mountains, stretching there in broad 

 plains, modified everywhere at the surface into fertile soils, 

 charged often at the depths with mineral treasures — the whole 

 a rich patrimony wasted on unintelligent aborigines until men 

 of thought and action came to claim it. Then, since the lands 



