298 Profefar WILLIAMS on Earthquakes. 
Thus, in the contents of the earth; we find fufficient matex 
rials for the. production of the moft ftrong, active and powers: 
ful vapour ;—and fuch- materials as do, in fa, produce moft 
terrible .volcanoes,—yvapours that have hove up, and broke thro’ 
the furface of the earth,—and earthquakes that have fhaken the 
whole country, for twenty miles-around Fefüvius and Zina. 
—And fuch explofions and concuffions are what all thofe coun- 
tries are. fubject to, which. abound. with fulphur,. nitre,. and: 
fach combuftible materials. - 
As the contents of the earth will'acccunt for the oriyin, the: 
Jtrutture of it will account for the motion and direction of a fab- 
terraneous vapour.. Were the globea perfect folid, there could- 
be no motion of a fubterraneous vapour under its dtrface. But 
this is not the. cafe.—Inftead. of being.a perfect folid, the earth: 
is of a cavernous Jiru&fure ; containing various pits, holes and: 
caverns,. Some of thefe are dry ; others are the fountains, or- 
contain currents of water ; and others abound with the fumes- 
of fermenting minerals; and-with-various kinds» of vapour and: 
effluvia. "That the earth isthus of a. cavernous ftru&ure, is 
evident. from the mines, . fprings, and currents of water, that: 
are found below its furface, in every country, and in almoft: 
every place. And it is probable, that many of thefe fubter-- 
raneous caverns may be of à great extent ;—íome- running 
in a dire&, and others in long, crooked, unequal paflages. 
~~-And by thus winding, meeting, crofüng and mixing with: 
each other, they may form communications between very 
diftant parts of the earth. The mazmer in which the folid. 
and fluid.parts of the earth are Zjpofod, is alfo worthy of 
| 1n {ome places, they are found promifcuoufly min- ` 
ended: together, in a manner which has no apparent 
ordet 
