1868. | Gold in California. 315 
amount of metamorphic action to which the enclosing strata have 
been subjected. 
The matrix of the auriferous veins of California is invariably 
quartz, which is usually crystalline, and, in the majority of cases, is 
ribboned in such a way as to form a succession of layers parallel 
with the enclosing walls. In some cases these parellel bands are 
separated from each other by a layer of quartz, differing slightly, 
either in colour or structure, from that forming the seams them- 
selves; whilst in others they can only be distinguished by the 
difference of colour of two adjoming members of the series. 
In many instances, however, lamine of the enclosing slates 
divide the vein into distinct bands, and in such cases the thickness 
of the interposed fragments is often not greater than that of writing- 
aper. 
i on addition to ordinary quartz, amorphous silica, or semi-opal, 
and chalcedony are sometimes met with; and this opal, which is 
interfoliated between the layers of true quartz, occasionally con- 
tains iron pyrites and metallic gold. The walls are in most in- 
stances smooth, and often afford evidence of a considerable amount 
of mechanical action, whilst between them and the vein itself a 
thin stratum of clay or flucan is sometimes interposed. 
In some of the detrital deposits of the gold regions distinctly 
marked quartz veins are observed cutting through the gravels, 
and are evidently formed by the action of water holding silica in 
solution. In certain localities also bands of silicious slates are 
found to contain small quantities of gold. 
Analysis has shown that the quartz constituting the matrix of 
the auriferous veins of California almost invariably gives off, on 
bemg heated to redness, a certain amount of water which is not 
eliminated by a prolonged exposure to a temperature of 212° F., 
and that, im addition to alumina, oxide of iron, and other impuri- 
ties, it always contains minute quantities of potash. On being 
reduced to the state of thin sections, for the purpose of examination 
under the microscope, the quartz is found to contain numerous small 
cavities partially filled with a liquid in which yacuities or gas- 
bubbles are seen to move about with great facility. 
Boiling and hot springs are exceedingly numerous throughout 
California and the adjoining state of Nevada; and in Steamboat 
Valley, about seven miles from Virginia city, a large quartz vein 
appears to be now in process of formation by hydrothermal agencies. 
The hot springs of this locality are situated at a height of 5,000 feet 
above the level of the sea, on the eastern declivity of the Sierra, 
and the granitic rock here presents several straight and parallel 
fissures, either giving exit to heated water, or simply ejecting steam. 
The first group of openings comprises five longitudinal crevices 
extending in a straight line, and parallel to each other, for a dis- 
