S. B. Christy— Genesis of Cinnabar Deposits. 461 
50,000 feet to give this temperature. At New Almaden, for 
example, which is certainly not in the immediate vicinity of 
volcanic rocks, since the cinnabar outcrops upon the summit o 
the hills, we should have to assume an erosion to have taken 
times as great as at present, it would still require a depth 
steam except by the presence of local igneous rocks. Pfaff, in 
his Geologie als Exacte Wissenschaft, p. 112, shows this by the 
following table. 
Temperature. Pressure of water | Tension of steam 
Depth in feet. Centigrade. in atmospheres, in atmospheres. 
10,000 100 300 
20,000 200 600 
80,000 800 2400 1416- 
100,000 1000 3000 1877" 
200,000 2000 6000 2403° 
The third column gives the weight in atmospheres of a col- 
umn ae water of a height equal to the depth; this is the mini- 
mum pressure to which it can be e ess we suppose 
an extensive fissure filled only with air and extending far up- 
ward. The fourth column gives tension of steam at the 
temperatures corresponding to the depths calculated according 
to Regnault’s formula. Itis evident that under these condi- 
tions the water will never boil at any depth except in cases of 
local eruptions of volcanic rocks. Although there have not 
