The Philosophy of Earthquakes. 359 



connected with movements of elevation, their operations are 

 often such as to cause the levelling power of water to counter- 

 act itself; and although the idea may appear paradoxical, we 

 may be sure whenever we find hills and mountains composed of 

 stratified deposits, that such inequalities of the surface would 

 have had no existence if water, at some former period, had not 

 been labouring to reduce the earth's surface to one level.* It 

 does not, however, follow that the average action of earthquakes 

 is one of elevation, although they are plainly connected with 

 movements that often have that effect. When there are great 

 hollows resulting from the outpouring of subterranean matter 

 by volcanoes and mineral springs, or from the solidification of 

 enormous masses of rock, severe shakings must tend to convey 

 matter from the surface towards the interior of such hollows, 

 and in such cases earthquakes will exert a depressing effect. 

 It is obvious that if actions of degradation went on for long 

 periods unchecked, the earth would become an uninhabitable 

 flat, while if the opposite movements of elevation were not coun- 

 teracted for an equally long period, the mean diameter of the 

 globe would increase, and the surface would become like a huge 

 irregular bubble, destined ultimately to sudden and disastrous 

 collapse. The existence of the animals and vegetables that 

 inhabit our globe is strictly, though by no means exclusively, 

 dependent upon the class of forces to which earthquakes belong, 

 and therefore Sir 0. Lyell is justified in affirming that "they 

 are agents of a conservative principle, above all others essential 

 to the stability of the system." 



The earth's permanence is the result of forces, every one of 

 which is engaged in destroying a previous condition of things, 

 and introducing a new one ; but which are so antagonised and 

 balanced as to leave it substantially the same. We need not 

 now speculate on those residues of unbalanced forces which 

 may ultimately change it altogether, as their operation is 

 infinitesimally slow, and can only become sensible after the 

 lapse of time-periods utterly beyond our grasp. They also 

 belong to the cosmos as a whole, and not specially to our minute 

 speck of it; and if our sun, with all his attendant worlds, should 

 ultimately pass into another form, it would no doubt be in 

 obedience to laws as conservative of the entire universe as 

 earthquake laws are conservative of our terrestrial sphere. 



If the reader has followed this argument, he will be pre- 

 pared to deal with earthquakes as phenomena of order, and to 

 learn that the exact calculations of the mathematician are 

 found applicable to them, so far as their conditions can be made 

 out. He will also be prepared to discriminate between actual 

 shocks or concussions, and the tumbling in, or slipping down 

 * 'Principles of Geology, 9tli edition, p. 56 ±. 



