206 Dr. Cooper on Volcanoes 
My volcanic and fletz trap collection consists of 
One case (about forty La neighbourhood of Roine. 
pe 
One Do. Italy and Spa 
man ny. 
One Do. Great-Britain and Ireland. 
One Do. The volcanic Mediterranean isles 
One Do. The volcanic African Islands, with the Isle of 
Bourbon 
One Do. The Wost-India Islands, and Ferro. 
One Do. Miscellaneous. 
-One Do. Minerals imbedded in volcanic matt 
One Do. Zeolytes of various kinds, and imbedded prehnites. 
One Do. Pseudo-voleanic products. 
One Do. American fletz cee" supposed volcanic ; North- 
E -Yor 
One Do. New-Jersey, esa and Carolina 
Which I ates for the sencpeipenad shewing that I have 
taken to ascertain the 
i y of origin, of voleanie ejections and ~ foots trap 
ON VOLCANOES AND VOLCANIC SUBSTANCES. 
On examining the Fag of the strata that compose the 
crust of the eart e find manifest proofs of deposition 
from aqueous fnictithe in some cases, and ejections from 
igneous fusion in others. Effects may have been produced 
by the agency of magnetic polarity, or Galvanic electricity ; 
but as we cannot point out any known appearances ascriba- 
ble to these causes, we must reject them. We can explain 
phenomena fiat are doubtful, only by means of phe- 
nomena that nown: nor is it allowable in our ae 
sophical relsonkibs to take for granted the actual existence 
of any agent, from the mere possibility of its existence. . A 
posse, ad esse, non valet conse 
Hence as we are unacquainted with any geological phe- 
nomena appertaining to the strata that form the crust yc 
_except such as are owing to the agency of water, oF 
th 1e ag Buy of fire, or the agency of both these causes com- 
d—we must confine ourselves in the prseeet.J state of 
pa An to these, the only known sources of expla- 
Pnteceee nero eso 
