124° Mr. Dana on the Analogies between the 
Thus far in our argument, I have endeavored to show that as iy a 
in those igneous regions where porphyries were formed, there are = 
metamorphic phorphyries, so in those igneous regions where gran- 
ites and the associated rocks were formed, there are metamorphic — i C 
granites, gneiss, &c.; and we have considered the evidences that = 
some granites, as well as some of the schistose associates, were 
originally of sedimentary origin, and have proved as we believe, 
that all talcose and chlorite rocks, steatites and serpentines, are 
undoubtedly metamorphic, and also some granular limestones. 
We have. also argued, and may I not say proved, that heated 
waters, both the transfused and superincumbent, set in motion by 
the eruption, have produced changes in rocks at all ages of the 
world, and in the same manner as sandstones have been altered 
and -filled with erystals, and porphyries remade, so the primary 
rocks have been recrystallized. Thus one and the same cause ex- 
plains all igneous changes, and Lyell’s grand principle, that exist- 
ing causes explain past phenomena, is carried out almost to the very 
letter. We can no longer say in the words of Lyell, speaking of these 
early rocks, that ‘part of the living language of nature has passed 
away, which we cannot learn by our daily intercourse with what 
passes on the habitable surface.” The language still lives—it is 
seen in every bed of once molten rock, that courses hill or plain 
throughout our globe ; it isread in the many traces of fire, im- 
pressed in crystal characters on limestone, sandrock or shale ; and 
is it not heard in those thunderings, muttered forth with the deep 
heavings of a hemisphere, which seem to tell of submarine erup~ 
tions, of ejected lavas beneath an unfathomed sea, of ignited re 
fountains opened and waters in commotion, hot with lava fires, n 
rushing through the rocks and over the regions around ?. 
In drawing the last analogy between volcanic rocks and gra- 
nitic, to which I would beg your attention at this time, Iam 
venturing still farther and more deeply into the dark ages of our 
globe. Yet there isa ray of light penetrating even this obscu- 
rity :—at least, the light of volcanic fires, by which midnight 
views may be taken, and some glimpses caught of the operations 
that moulded a forming world, ‘ % np 
In the volcanic regions of these modern days, as well as those 
of times past, when the fires now extinct were burning, the outer 
limits of the region of igneous action are more generally strati- 
fied, and more abound in tufas or. sedimentary deposits than the 
