218 The American Geologist. April, i89i 
especially when slate, bent away from the normal dip, correspond- 
ing -with that of the vein ; hence, it is probable that the hanging 
wall has been pushed up. If this is the case it would indicate an 
upward strain along the mountain range which tended to relieve 
itself in the fissure of the lode. 
That the lode is a true fissure vein is amply proved by the 
universal presence of gouge seams. The movement of the walls of 
some of the fissures has been immense. This is made easy on ac- 
count of their length. The great width of ground-up wall rock 
and quartz, sometimes forty feet, indicates a long continuance of 
the movement, probably more or less oscillatory, and with a 
general rise of the hanging wall. The greatest depth to which the 
lode has been opened (twenty-two hundred feet) shows no weaken- 
ing of the vein or deterioration of the ore. It is not likely that 
any great degree of heat would be encountered at any depth that 
could be reached, for thus far no increase in temperature has 
been noticed. 
In stiKtying the occurrence of gold and its ores in the Mother 
Lode, no relation has yet been found to exist between the char- 
acter of the walls and the poverty or richness of the quartz. It 
is recognized that a vein lying at the contact of two dissimilar for- 
mations is more regular, and that the mineral contents are more 
easily distributed than in one lying in a formation which does not 
easily afford a regularly defined fissure. 
I do not believe that in the case of the Mother Lode, the min- 
eral character of the walls has influenced the deposit ; that is, in 
the sense of the mineral contents having been derived directly 
from them. The mines of the lode are equally rich whether in 
slate or at the contact of slate with diabase, diorite, or serpentine ; 
and poor mines may be found with any of these conditions. 
I do not think that any combination of wall rock will insure a 
rich vein, but that the deposit of the metallic particles is depend- 
ent more upon certain chemical reactions taking place in the solu- 
tions or vapors circulating in the fissure. This is proved by the 
fact that of two veins lying side by side in the same mine, one may 
be barren while the other constitutes the pay rock. What appears 
as walls on the surface or at any depth which can be reached is no 
indication whatever of the character of those deep-seated portions 
from which the circulating fiuids abstracted their mineral contents. 
The real conditions are certainly complex, differing greatly in 
