364 The American Geologist. J""^- ^^^^ 
But is there no gold in Iowa ? ]\Ien certainly have found 
some. Coal occurs in certain localities in the state, why are 
the chances not equally good for finding it in all other local- 
ites? Why is it not a good business venture in Iowa to ex- 
plore the depths of the earth for gas and oil. when fortunes 
are made and cities are boomed by the discovery of these de- 
sirable products in other states ? Why is it not a proper func- 
tion of the Geological Survey to bore test holes in different 
localities in order to settle the question of the presence of oil and 
gas beneath the surface? To answer these questions fully 
would require much space and would involve a discussion of 
some of the most elementary principles of geology. Let me 
trv as briefly as possible to present the facts necessary to an un- 
derstanding of these subjects for the benefit of the non-geolog 
ical reader. 
Xative gold, metallic gold, free gold — by whatever name it 
may be designated — occurs chiefly under two conditions. First, 
it is found in veins in the crystalline rocks. Such rocks are 
generally very old ; they are fundamental : they occur at the 
surface in a broad belt around Hudson Ray — none of the new- 
er or later formed rocks being present in that locality — and 
they extend down into northern Michigan, northern Wisconsin 
and northern JMinnesota. They have been forced up near tlie 
surface and have been subsequently exposed by erosion in all 
mountain regions. As a rule, it is in mountain regions that 
gold is associated with them, for it is here that they have been 
fissured by the strains and movements which gave rise to the 
mountains. A'arious minerals have been concentrated in the 
fissures by circulating waters — the waters being more efficient 
if w^arni and alkaline — and among the minerals so concentrated 
we sometimes find gold. Gold-bearing veins in the crystalline 
rocks are the basis of all the lode mining; but it must be kept 
in mind that only a very small proportion of all the veins re- 
ferred to carry gold. Xow there are no true crystalline rocks 
anywhere near the surface in Iowa. All such rocks here are 
deeply covered with newer rocks of sedimentary origin. These 
sediments were laid down, one on the other, in slow and order- 
ly succession, on ancient sea bottoms, in precisely the same way. 
and of precisely the same materials as the beds of mud and sand 
and limy ooze which are to-day accunmlating on the marginal 
