330 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. 



the surface. I have shown that the deposits were probably induced by 

 volcanic acti\'ity following the eruption of this lava, so that a not very 

 remote connection exists between the ore-bearing fissures and that marked 

 by rhyolite. At the time of the lava eruption the present range of hills 

 existed much as it does to-day. Consequently the course of a fissure tend- 

 ing to assume a strike nearly parallel to that of the dike and which was 

 formed near the range of the hills would be affected by their presence. 

 The hills would act as a mass of considerable rigidity and would tend to 

 deflect such a fissure, but if at any point this tendency were overcome the 

 fissure would return more or less closely to the direction of the dike. Now, 

 near the Guadalupe the line connecting the deposits is almost exactly par- 

 allel to the dike ; as the ridge curves away from the dike the line of de- 

 posits follows the high ground. After the angle between the ridge and the 

 dike becomes large the line of fissure seems to me to cross the higli land 

 and to approach the dike again in the New Almaden ground at an angle of 

 about 30°. In crossing the ridge a branch fissure seems to have been 

 formed leading to the Washington. 



I cannot, of course, pretend to have demonstrated the above explana- 

 tion of the relations of the deposits. For this the exposures are insufiicient. 

 I off"er it, however, as a working hypothesis which possesses considerable 

 probability and may serve as the basis for a more exact tlieor}' to be elab- 

 orated by the engineers in charge of the properties. It is probably needless 

 to remark that if the hypothesis set forth above be true it shows where ore 

 is to be sought, but ore will be found only at certain favored points or in 

 certain channels at or near the fissures. If the Washington fissure actually 

 meets that connecting the New Almaden and the America, great disturbances 

 must have taken place at the junction and some ore will probably be found 

 there. 



