BABBAGE ON THE TEMPLE OF SERAPIS. 2()9 



for new deposits, which will, in their turn, become similarly con- 

 solidated. But the surface of uniform temperature below the bed 

 of the ocean, cannot rise towards the earth's surface, without an in- 

 crease in the temperature of all the beds of various rock on which it 

 rests ; and this increase must take place for a considerable depth. 

 The consequence will be a gradual rise of the ancient bed of the 

 ocean, and of all the deposits newly formed upon it. The shallow- 

 ness of this altered ocean will, by exposing it to greater evaporation 

 from the effect of the sun's heat, give increased force to the atmo- 

 spheric causes still operating upon the inequalities of the solid surface, 

 and tend more rapidly to fill up the depressions. 



89. Possibly the conducting power of the heated rocks may be so 

 slow, that its total effect may not be produced for centuries after 

 the sea has given place to dry land ; and we can conceive in such 

 circumstances, the force of the sun's rays from without, and the in- 

 creasing heat from below, so consolidating the surface, that the land 

 may again descend below the level of the adjacent seas, even though 

 its first bottom is still subject to the elevatory process. Thus, a series 

 of shallow seas or large lakes might be formed ; and these processes 

 might even be repeated several times, before the full effect of the 

 expansion from below had permanently raised the whole newly- 

 formed land above the influence of the adjacent seas. 



If the whole sea, or particular portions of it, were originally much 

 deeper, as, for instance, ten or twenty miles, then a portion of the 

 solid matter beneath its surface might, after a lapse of many ages, 

 acquire a red, or even a melting heat, and the conversion into gases 

 of some of the substances thus operated upon might give rise to 

 earthquakes, or to subterranean volcanos. 



90. On the other hand, as the high land gradually wears away by 

 the removal of a portion of its thickness, and as the cooling down of 

 its surface takes place, its contraction might give place to enormous 

 rents. If these cracks penetrate to any great reservoirs of melted 

 matter, such as appear to subsist beneath volcanos, then they will be 

 compressed by the contraction, and the melted matter will rise and 

 fill the cracks, which, when cooled down, become dykes. Rents 

 therefore or veins may arise by contraction from cooling, and pro- 

 ceed from the surface downwards ; or they may result from expansive 

 forces acting from below and proceed upwards. 



If these rents do not reach the internal reservoir of melted matter, 

 and if there exist in the neighbourhood any volcanic vents connected 

 with it, the contraction of the upper strata may give rise to volcanic 

 eruptions through those vents, which might be driven by such a force 

 almost to any height. These eruptions may themselves diminish the 

 heat of the beds immediately above the melting cauldron from which 

 they arise ; for the conversion of some of the fluid substances into 

 gases, on the removal of the enormous pressure, will rapidly abstract 

 heat from the melted mass. 



As the removal of the upper surface of the high land will diminish 

 its resistance to fracture, so the altered pressure arising from the 

 removal of that weight, and its transfer to the bottom of the ocean, 



