“Geology and Natural History. ae 
remarking that the problem of the origin of those rocks, both 
stratified and unstratified, which are made up chiefly of crystal- 
line silicates, is essentially a chemical one. He then proceeded 
to review the dispute between the vuleanist and the neptunist 
schools in geology, as to whether granite and other crystalline 
rocks were formed by igneous or by aqueous agencies, and 
showed from recent writers that the controversy is not yet 
settled. He noticed, of the igneous school, both the plutonic and 
the volcanic hypotheses of the origin of these rocks, and then con- 
sidered the so-called metamorphic and metasomatic hypotheses, 
which would derive them by supposed chemical changes from 
f 
these rocks. The ay of all of these hypothese was. 
pointed out, though it would appear that Werner’s was the one 
nearest the truth. 
The author conceives that the crystalline rocks were formed by 
ee from waters which successively dissolved and brought 
m subterranean sources the mineral elements. Their formation 
is ‘itamtete by that of granitic veins, and that of zeolites,—pro- 
cesses regarded as survivals of that which produced the earlier 
rocks. The true zeolites are but hydrated feldspars, while the 
minerals of the pectolite group correspond to the rel lps 
cates of the ancient rocks. The sources of the elements in t 
rocks, according to the new hypothesis here proposed, was in the 
superficial layer which was the last-congealed portion of an igne- 
us globe, consolidating from the center. In this primitive 
‘Stratum, porous from contraction, and impregnated with water, 
resting upon a heated anhydrous nucleus, and cooled by radia- 
tion, an aqueous circulation ick e set up, giving rise to 
mineral springs. The waters of these dissolved and brought to 
the surface, then to be deposited, the quartz, the feldspars, and 
other mineral silicates, which through successive ages built up 
the great gr oups of crystalline stratified rocks, often so markedly 
Soest d in aspect. Exposed portions of the primitive sil1- 
ted material would be subject to atmospheric decay and disin- — 
searatien, givin sediments of superficial origin, which 
rise to 
would become intercalated with the deposits from subterranean 
and the superficial materials were important in this connection, — 
probabl iving rise to certain common micaceous mi inerals,— 
while dissolved silicates allied to pectolite, by their reaction with 
e€ magnesian salts, which then passed in = the ocean-waters, 
generated species s like serpentine and pyro 
This process of continued upward lceviantons of the primitive 
chaotic stratum would result in the production of a = over- 
phate met of stratified arentine rocks, leaving below a nee, 
