EARTHQUAKE-PHENOMENA. 525 



which melts the great lava-beds, and fills cavities in the earth's crust 

 with steam and gases, may not arise directly from the earth's central 

 heat, but from the crushing of strata as it contracts and settles upon 

 the cooling interior. 



By a series of experiments and observations made by Mr. Mallet, 

 it is shown that the " annual loss of heat into space of our globe at 

 present is equal to that which would liquefy, at 32 Fahr., about 777 

 cubic miles of ice; and this is the measuring unit for the amount 

 of contraction of our globe now going on." 



The amount of shrinking depends, therefore, on the amount of heat 

 lost a view long since insisted on by Prof. Dana ; and this, according 

 to Mallet, is sufficient to account for all the phenomena. To this cause, 

 then, we refer the never-ending oscillations of the earth's cooled ex- 

 terior, and the enormous lateral strain by which it is bent and frac- 

 tured, and its broken ridges made to grind and crush with terrific 

 vibrations. 



In many areas the earthquake energies of former times have been 

 long at rest, but, according to Sir Charles Lyell, the total energy 

 may not have diminished. 



He finds evidence of convulsions as great and obvious in recent as 

 in earlier time. Mallet, however, remarks that " seismic energy may 

 be considered as possibly constant during historic time, but is probably 

 a decaying energy viewed in reference to much longer periods." 



Everywhere we see, in exposed portions, crevices open or filled 

 ejections of trap and basalt ; and wall-like dikes stand out upon the 

 slopes of mountains. These are legible and significant chapters in the 

 earth's dynamic history. 



Do earthquakes occur with any order or system, so that their 

 coming may be foretold ? 



Prof. Palmieri, in his observatory on Mount Vesuvius, is able, says 

 George Forbes, " to predict eruptions." " This is a small eruption," 

 remarked the professor, " but there is going to be a greater one ; it 

 may be a year hence, but it will come." " In almost exactly a year," 

 continues Mr. Forbes, " the great eruption did come." 



From Mallet's catalogue of European earthquakes it appears that, 

 during 15 centuries, 1,157 took place during the winter, against 875 

 in the summer months. 



Although science has cleared up some of the mystery which hung 

 over earthquakes in less enlightened times, it has not divested them of 

 their sublimity and terrible reality. 



Their work of destruction is done in a moment. The great battles 

 of the -world have scarcely been so destructive of human life. 



We read that 250,000 persons perished during the earthquake at 

 Antioch in 526. At Lisbon 60,000 people were destroyed. During 

 one of the Calabrian earthquakes 35,000 ; and during the one at Are- 

 auipa in 1868. 40.000 persons perished. Pestilence, famine, and fire. 



