58 QUICKSILVER DEPOSITS OF THE PAOIFIC SLOPE. 



Hypotheses. — Studeiits of tliG extreiTiely difficult subject of metamorpliism 

 have, no doubt, in some cases been tempted to put forward hypotlieses, to 

 account for tlie existence of crystalline rocks, vvhicli were warranted neither 

 by detailed oliservation oii the actual series of changes nor by any known 

 chemical principles. It would be a great mistake to assume, howevei', ih it 

 carefid observations on actual ti-ansformations are valueless uidess they 

 can be accounted for by known chemical relations. Even the structural 

 formulas of many most important minerals are still in doubt; much more so 

 is the complete theory of their formation; while recent researches, particu- 

 lai-ly those of Dr. Wolcott Gribbs, demonstrate the extreme complexity of 

 many inorganic chemical processes. Though there can thus be no question 

 as to tlie existence of transformations in altering rock masses for which no 

 adequate explanation can be offered, it is equally true that observed facts 

 are frequently capable of two or more explanations and that the relations 

 of mingled products are often susceptible of misinterpretation. In the 

 present investigation great care has been taken to avoid errors; and sev- 

 eral hypotheses as to relations, in support of which considerable evidence 

 can be adduced, have not been admitted on the ground that the appear- 

 ances might after all be deceptive. It is believed that by this means the 

 errors have been reduced to a minimum and that the residual observations 

 and inferences recorded in the following pages afford a solid foundation 

 for future inquiry. The results also seem sufficiently definite to form an 

 important aid in the study of more complex metamorphic areas in other 

 parts of the world. That the conclusions reached are applicable to other 

 portions of California is almost certain, for the metamorphosed rocks of 

 the gold belt are in part of the same age as those of the Coast Ranges 

 and appear to be strikingly similar in lithological character. That region 

 is now under investigation ])y my l)art3^, and it is believed that further 

 interesting results, for the same class of metamorphic rocks at least, will be 

 obtained in the near future.^ 



' It is probably impossible for any one to free himself fi'om the iutlueuce of preconceptions. It 

 may not be superfluous, therefore, to state that in beginning the investigation of the quicksilver belt I 

 entertained no opinions ou the character of the crystalline auil serpentiuoid rocks. I was quite pre- 

 pared to find the former either eruptive or unaltered crystalline sediments and I entertained no preju- 

 dice against regardiug serpentine either as an original deposit or as an altered olivine rock. I still 

 regard it as not improbable that crystalline schists and serpentine are sometimes original precipitates 



