Origin of tJic Arclican Igneous Rocks. — IVi/ichc/l. 303 
Such waters having an extraneous source their mineral 
character must also have had a foreign origin. They could 
not at least have been derived from the diabase, since the chief 
deposits are not in the diabase rock, but in a coarse conglom- 
erate — and if from the diabase, on this evidence, then in nuich 
greater quantity from the acid conglomerate. 
Therefore, if mineral solution from a foreign source de- 
posited metallic copper at the sixth stage of the process, how 
much more likely that orthoclase, at the twelfth stage, was also 
generated by mineral solutions from an extraneous source, 
neither of these substances being indigenous in diabase. 
It may still be claimed that all, or at least many, chem- 
ical analyses of diabase show the presence of a small amount 
of potassium which may have been sufficient at least to 
generate the orthoclase seen in the veins and geodes. Sup- 
pose that be admitted, it still demonstrates nothing. Such 
potassium found in diabase, or even in a sod?-lime feldspar, 
is always accompanied by a certain percentage of water, as 
testified by chemical analyses, and the presence of water points 
to a certain amount of decay and the introduction of foreign 
ingredients. Theoretically there is no hygroscopic water, and 
no potassium in any of the minerals of a pure diabase. If 
water, potassium and metallic copper be found, on analysis, to 
exist in a certain diabase, they may all be considered equally 
as of later introduction from a foreign source, and they, there- 
fore, could have had no agency in the supposed widespread 
transformation of the ferro-magnesian magma to an alkaline 
one. 
Hence the principal evidence of Hunt for the leeching of 
potash by any sort of "fermentation," such as assumed by the 
crenitic hypothesis, and the generation of orthoclase, and 
hence of all the alkaline silicates, from a ferro-magnesian mag- 
ma, seems to be inadmissible. If the principal step in support 
of the crenitic hypothesis is found to be unwarranted, all the 
subordinate and secondary steps in that process are rendered 
insecure and purposeless. 
This dif^culty also stands obviously against all other livjio- 
thetical processes of derivation of the alkaline-acid magma 
from the ferro-magnesian, whether by differentiation at the 
surface or in deep reservoirs, and the idea of such origin of 
