206 Dr. Cooper on Volcanoes 
My voleanic and fleetz trap collection consists of 
One case (about forty specimens) neighbourhood of Rome. 
One Do. Italy and Spain. 
Two Do. France. 
One Do. Germany. 
One Do. Great-Britain and freland. 
One Do. The volcanic Mediterranean isles... . 
One Do. The volcanic African Islands, with the Isle of 
Bourbon. 
One Do. The West-India Islands, and Ferro. 
One Do. Miscellaneous. pares 
One Do. Minerals imbedded in voleanic matter. ) 
One Do. Zeolytes of various kinds, and imbedded prelinites. 
One Do. Pseudo-volcanic products. 
One Do. American flcetz trap, supposed volcanic; North- 
East of New-York. , sal ‘ua 
One Do. New-Jersey, Pennsylvaniaand Carolina. ___ 
~ Which I mention, for the purpose of shewing that I have 
taken much pains in collecting specimens, to ascertain the 
identity of origin, of volcanic ejections and the fletz trap 
formation. 
ON VOLCANOES AND VOLCANIC SUBSTANCES. 
Ow examining the structure of the strata that compose the 
crust of the earth, we find manifest proofs of deposition 
from aqueous mixture 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 that are doubtful, only by means of phe- 
nomena that are known: nor is it allowable in our philo- 
sophical reasonings, to take for granted the actual existence 
of any agent, from the mere possibility of its existence. 4 
posse, ad esse, non valet consequentia. 
Hence as we are unacquainted with any geological phe- 
nomena appertaining to the strata that form the crust of the 
earth, except such as are owing to the agency of water, or 
the agency of fire, or the agency of both these causes com- 
bined—we must confine ourselves in the present state of 
our knowledge, to these, the only known sources of expla- 
