204 KANSAS CITY REVIEW OF SCIENCE. 
of various kinds of igneous rock, mingled with which in the latter are masses of 
silicified wood and charcoal; while in the Carbonate mine, the pebbles are mainly 
trachyte ; but with these are others of limestone and quartzite. 
Fossils and other foreign bodies have before this been found in mineral veins, 
and Von Cotta mentions the occurrence of quartz pebbles extending to the depth 
of 155 fathoms in the Griiner Lode at Schemnitz, Saxony; but no conglomerate 
veins like those mentioned above are known to exist elsewhere, and they consti- 
tute another of the many new forms of ore deposit which the exploration of the 
rich and varied mineral resources of the United States has brought to light. To 
enumerate and classify these, has been the chief object of this article. 
In regard to the ultimate source of the metallic matters which give value to 
our ore deposits, but little can be said with certainty. The oldest rocks of which we 
have any knowledge, the Laurentian, contain gold and copper, which are indig- 
enous, hence as old as the rocks that contain them, and have been simply con- 
centrated and made conspicuous in the process of their metamorphism. ‘These 
rocks are all sediments and the ruins of pre-existing continents. By their ero- 
sion, they have in turn furnished gold, copper, iron, etc., to later sediments by 
mechanical dispersion and chemical solution. We now find gold everywhere in 
the Drift from the Canadian Highlands, and we have every reason to believe that 
all the sedimentary strata more recent than the Laurentian have acquired a slight 
impregnation of several metals from them in addition to what they have obtained 
from other sources, and we may conclude that the distribution of many of the 
metals is almost universal. Sea-water has been proved to contain goid, silver, 
copper, lead, zinc, cobalt, nickel, iron, manganese and arsenic; and there is lit- 
tle doubt that all the other metals would be found there if the search were suffi- 
ciently thorough. Hence, sedimentary rocks of every age must have received 
from the ocean in which they were deposited some portion of all the metals, and 
for the formation of metalliferous deposits some method of concentrating these 
would alone be required. A pretty theory to explain such concentration through 
the agency of marine plants and animals has been suggested by some German 
mineralogists, and amplified by Professors Pumpelly and T. 5. Hunt. Plants have 
been credited with the most active agency in this concentration; but evidence is 
still wanting that either plants or animals have played any important part in the 
formation of our mineral deposits. The remains of sea-weeds are found in the 
greatest abundance in a number of our Paleozoic rocks, and it is almost certain 
that the carbonaceous ingredient in our great beds of bituminous shale has been 
derived from this source; yet we find there no unusual concentration of metallic 
matter, and none of the precious metals has ever been detected in them. 
The metallic solutions which have formed our ore-deposits have been ascribed 
to two sources. One theory supposes that they have drained highly metalliferous 
zones deep in the interior of the earth; the other, that they have leached diffused 
metals from rocks of different kinds comparatively near the surface. The latter 
view is the one that commends itself to the judgment of the writer. However 
