Wadsworth.] 
98 
[November 17, 
forming; stalactites in basaltic caverns. * * * * * These facts favor 
throughout the view we urge that amygdaloidal minerals have in general 
resulted from infiltration, and were not necessarily formed simultaneously 
with the erupted rock. We remark farther, that no lavas have ever been shown 
to contain at the time of ejection, any of the zeolitic minerals. * * * * * 
* * Zeolites also have been found disseminated through the texture of 
basalt, clinkstone, &c., like the feldspar, augite, &c. But the proportion 
varies widely, and in some parts of the same bed they are found to be want- 
ing; so that we have sufficient reason for classing these disseminated zeolites 
with those in the cavities, as formed or introduced by infiltration. * * * it 
should be observed, that the constituents of amygdaloidal minerals are, in 
general, those of the containing rock. * * * * With water to infiltrate, we 
should therefore have all the necessary ingredients at hand for the required 
compounds. The fact already stated, that zeolites have been found as sta- 
lactites in caverns, seems to prove that they do actually result from decom- 
positions and recompositions, such as have been supposed. Thus we have 
all the conditions at hand necessary for producing, by infiltration, the zeo- 
lites and the chlorite nodules of these rocks. * * * * The hypothesis of 
filtration seems, then, to be at least the principal source of these minerals. 
***** What is the condition of the deep bed of an ocean ? Even at 
a depth of three miles, the waters press upon the bottom with a force 
equivalent to a million of pounds to the square foot; and with such a for- 
cing power above, can we set limits to the depth to which these sea waters 
— magnesia and soda solutions — will penetrate? Will not every cavern, 
every pore, far down, be filled under such an enormous pressure? * * * 
****** We are led by these considerations to another point in con- 
nection with this subject: the probable condition under which the different 
amygdaloidal minerals have been formed. Have they all proceeded from 
heated solutions, or all from cold solutions ? * * * * * Many of them may 
require heat, and some may be the last depositions from the filtrating waters 
after they have nearly or quite attained their reduced temperature, but the 
formation of zeolitic stalactites in caverns favors the view that some at 
least may form at the ordinary temperature by the slow decomposition of 
the containing rock after it had emerged from the waves. * ***** * 
* * In the above explanations we have scarcely appealed to one source of 
amygdaloidal minerals admitted in the outset — their proceeding from 
vapors rising with the erupted rock ; for it seems to be of but limited influ- 
ence. Besides the arguments already brought forward, we state that the 
vapors which rise at the moment of eruption are insufficient. They 
inflate the rock, or blow up the cavities ; but the little vapor required to 
open the cavities most assuredly could not afford by condensation the min- 
eral matter necessary to fill them, — to produce stalactites, stalagmite and 
