112 
IDDINGS. 
In 1880 Dutton * advanced a theory for the eruption and 
succession of volcanic rocks which differs almost entirely 
from any of those heretofore mentioned. It starts on the 
assumption that the average composition of the foliated 
rocks on the surface of the earth is very nearly the same as 
that of basalt, with the exception of the iron oxide. 
As to basalt, he says: “In truth, its whole range of char¬ 
acters is indicative of an origin among magmas which have 
never passed through the reactions and mechanical pro¬ 
cesses which prepared and arranged the materials of the 
sedimentary strata. Lastly, the basalts are among the most 
abundant of eruptive rocks, and, if we reckon with them 
the more ancient dolerites or diabases, they have always 
been abundant in all ages as far back as our knowledge 
extends; but not only should we infer that the primordial 
masses of the earth (or “ primitive crust ”) were basic like 
the basalts or dolerites, but that they were very nearly 
homogeneous.” The latter condition, he thinks, would have 
been brought about by the vast currents within the molten 
mass, which would have kept it thoroughly mixed. 
“We know of no natural processes capable of separating 
the more acid parts of such a magma, except the chemistry 
of the atmosphere acting at temperatures far below the melt, 
ing points of the silicates. We have the results of that pro¬ 
cess in the quartzites, granites, gneisses, and syenites among 
the silicious rocks, and the limestones and dolomites among 
the basic rocks, with argillaceous rocks as the residuum of 
the decomposition.” * * * “No facts are known to me 
which justify the conclusion that segregation into two mag¬ 
mas could occur in such a state of fusion.” 
In commenting upon King’s theory of crystallization and 
separation by differences of specific gravity, he considers it 
“ extremely doubtful whether any crystals are formed while 
the rocks are melted, and very probable that the greater part 
of them are formed during the viscous stage of cooling.” 
* Dutton (C. E.) Geology of the High Plateaus of Utah. 4°. Wash¬ 
ington, 1880, pp. 123 et seq. 
