9^ Applications of the Igneous Theory of the Earth. 



present us with islands or submarine mountains, according to 

 their elevation relatively to the oceanic surface. These inclined 

 portions of the earth's crust, resting on the central fluid of greater 

 specific gravity than themselves, and pressed firmly together at 

 their lower angles by their own weight, constitute the bed of 

 ocean and the principal marine divisions. 



If these are legitimate deductions from the geological theory, 

 it is manifest that by virtue of the gradual contraction of the 

 central fluid, the inequalities of the earth's surface are from age 

 to age increasing ; that in the gross, the elevation of continents 

 and islands above the surface of the ocean is gradually becoming 

 greater ; that the land is encroaching upon the water, or in other 

 words, that the level of the sea is from time to time assuming a 

 lower position with reference to fixed points on the shore. I say 

 in the gross, for partial causes may operate to vary the result in 

 particular cases ; and even extensive lines of coast may be so 

 situated as to exhibit the contrary phenomenon. On the princi- 

 ples of the theory, however, the general rule must be as stated. 

 Indeed, in view of the local evidences of this recession of the 

 waters, nothing is now more common with the geologist than to 

 assign, as a cause of the phenomenon, the " upheaving" of the 

 contiguous portion of the earth's surface. These are but par- 

 ticular cases under the general law. By way of illustration we 

 may refer to those islands whose soil rests on a continuous sub- 

 stratum of coral. Now it is well known, that the coral formation 

 is of submarine origin, and its appearance above the surface can 

 be accounted for only by the " upheaving" of the apex of the 

 submarine mountain on which its growth took place. 



The fragmentary character of the earth's crust would seem to 

 be strongly attested by the phenomena of earthquakes. These 

 phenomena, in all their extent and variety, are wholly irrecon- 

 cilable with the supposition that the structure of the earth is solid 

 throughout. And adopting on the other hand the hypothesis 

 of an unbroken and sulf-sustained shell, enclosing a central fluid, 

 it would be difiicult to avoid the conclusion that all earthquakes 

 must be universal in their extent. Physical action commencing 

 in any part of the shell, could hardly fail to send its vibrations 

 through the whole. It is matter of experience, however, that 

 these phenomena are not thus universal. Some are of compara- 

 tively small extent, while others affect considerable portions of 



