82 phou’oJjITic rocks. 
difficulty seems to arise from the too intimate and too 
numerous relations observed in rocks that are thought not 
to belong to the same family. 
The phonolite (or leucostine compacte of Cordier) is pretty 
generally regarded by all who have at once examined burn- 
ing and extinguished volcanos, as a flow of lithoid lava. I 
found no real basalt or dolerite; but the presence of 
pyroxene in the amygdaloid of Parapara leaves little doubt 
of the igneous origin of those spheroidal masses, fissured, 
and full of cavities. Balls of this amygdaloid are enclosed 
in the griinstein; and this griinstein alternates on one 
side with a green slate, on the other with the serpentine 
of Tucutunemo. Here, then, is a connexion sufficiently 
close established between the phonolites and the green 
slates, between the pyroxenic amygdaloids and the serpen- 
tines containing copper-ores, between volcanic substances 
and others that are included under the vague name of 
transition-traps. All these masses are destitute of quartz 
like the real trap-porphyries, or volcanic trachytes. This 
phenomenon is the more remarkable, as the griinsteins 
which are called primitive almost always contain quartz in 
Europe. The most general dip of the slates of Piedras 
Azules, of the griinsteins of Parapara, and of the pyroxenic 
amygdaloids embedded in strata of griinstein, does not follow 
the slope of tho ground from north to south, but is pretty 
regular towards the north. The strata incline towards the 
chain of the coast, as substances which had not been in fusion 
might be supposed to do. Can we admit that so many al- 
ternating rocks, imbedded one in the other, have a common 
origin? The nature of the phonolites, which are lithoid 
lavas with a feldspar basis, and the nature of the green slates 
intermixed with hornblende, oppose this opinion. In this 
state of tilings we may choose between two solutions of the 
problem in question. In one of these solutions the phono- 
lite of the Cerro de Elores is to be regarded as the sole 
volcanic production of the tract ; and we are forced to unite 
the pyroxenic amygdaloids with the rest of the griinsteins, 
in one single formation, that which is so common in the 
transition-mountains of Europe, considered hitherto as not 
volcanic. In the other solution of the problem, the masses 
of phonolite, amygdaloid, and griinstein, which are found 
