THEORY OF EARTHQUAKES—MAURY. 477 
Without desiring to exclude this as a possible cause of earth- 
quakes, I incline much more strongly to the theory which 
connects earthquakes and volcanoes as closely related phenomena, 
— both mainly due to one cause, viz.: the explosive force of 
enormous volumes of superheated steam. The difference between 
the two, I believe to be largely this,—that in the case of volcanoes 
there usually is a vent already existing, while in the case of 
earthquakes there is none. My idea (not however at all exclus- 
ively my own) is, that water, percolating through the crust of 
the earth, finding its way from some superficial source, the ocean 
or a river, far down into the interior of the earth, encounters 
intense heat. It meets with those very elements in a state of 
incandescence or of fusion, which form the slag of the casting 
pot. It is not necessary that the water in question should 
descend to the depth of more than 2,000 or 3,000 feet to encounter 
such heat. If you walk a few hundred feet down into crater of 
Vesuvius, you will soon find the soles of your feet uncomfortably 
warm, while from orifices in the walls of the crater hot jets of 
gas suggest to you that there must be somewhere near, a blowing 
engine of enormous capacity unweariedly driving its current of 
heated gas. And if you descend into the shaft of the famous 
silver mine near Virginia City, you will find the heat at. 
the depth of 2,500 feet so intense that the workmen labor 
almost naked, that they can work only a few hours at a time, 
and must have ice to apply every now and then to their wrists 
to keep down the temperature of their bodies. Between the 
strata of rocks situated near the scene of an earthquake, or near 
a volcano, especially if such strata are tilted, it requires no stretch 
of imagination to understand how water from the sea or river 
bed may glide into lower regions, where the materials of which 
rocks are made are in the molten state. A volcanic eruption or 
an earthquake would be the natural and necessary consequence. 
I consider that this view receives corroboration from the fact 
that volcanic regions are generally in seaboard regions. Vesuvius, 
Stromboli and AXtna, the long line of Andean volcanic heights 
which bristle along the Pacific coast of South America, the 
volcanoes of Krakatoa, and her companions in the Eastern Archi- 
