18 State of Earth’s Interior. 
The geologist observes the lines of volcanoes girdling the earth 
as it is, and concludes that there must be a very extensive ocean of 
molten matter beneath Earth’s crust, to say the least. 
He turns his attention to the great continents with their moun- 
tain ranges, high plateaus and low broad valleys, and finds a 
somewhat astonishing degree of instability everywhere. Up- 
heavals and submergences are everywhere in progress. From 
these signs he argues, and that rightly, that there must be a trans- 
lation of matter from point to point beneath the surface. 
‘This, he further argues, is consistent with fluidity only. A very 
legitimate conclusion surely. 
He takes another line of observations. He descends into the 
crust of the earth, and everywhere finds the temperature augmenting 
as he descends. Though this augmentation is constant, the rate of 
increment is not in all places the same. Still, however, this 
universal fact of increase of heat points straight to one conclusion, 
and corroborates the conclusion drawn from volcanoes, elevations 
or upheavals and submergences, viz., the temperature of liquefaction 
must be reached. All known rocks must become fluid. 
He turns to the record Earth has kept of her past history. 
There he finds that, in all geologic history, upheavals and sub- 
mergences have been common everywhere. He finds volcanoes 
have always existed. Moreover, he finds that great gaping rents 
have lacerated Earth’s adamantine bosom, and that through these 
huge rents vast streams of molten matter from the interior have 
gushed out over land and into ocean, spreading devastation wherever 
it flowed. | 
He now discovers that this molten condition of the interior has 
remained a persistent fact from the very earliest geological eras— 
undetermined millions of Earth’s years—zmillions, not thousands. 
Millenniums are but days in this great record. Interior heat has, 
therefore, been a persistent fact, and a persistent factor in geologic 
dynamics. , 
Moreover, these facts of upheaval and submergence, being 
universal, declare the universal fluidity of the great Earth-heart 
within. It is no circumscribed lake, as suggested by some. It is 
one universal mass of excessively high temperature. 
When, however, the geologist concludes that fluidity will be 
reached at about the point indicated by his observed rate of 
augmentation of temperature, along a descending line, his con- 
