PREFACE. 



The field work of the investigations recorded in tliis volume occupied 

 nearly the whole of three seasons, beginning in 1883. All the mines might 

 have been examined and the maps colored in a much shorter time, but it 

 was found soon after the examinations were begun that they could not be 

 completed satisftictorily without also solving some important general prob- 

 lems affecting. the whole region, and much of the time spent was devoted 

 to these questions. 



The examinations of the Knoxville and New Idria districts furnished 

 me with strong paleontological and structural grounds for believing that 

 an important and previously undetermined non-conformity existed in the 

 Coast Ranges. On my application, Dr. C. A. White devoted one season to 

 examining my collections of fossils and their field occurrence with me. He 

 indorsed my conclusions in all respects. The paleontological statements 

 of this report are all on his authority, excepting where otherwise accredited. 



It was found that the quicksilver districts of California afforded a re- 

 markable opportunity for the investigation of the metamorpliism of Meso- 

 zoic rocks and that it was highly desirable to determine what connection, if 

 any, existed between the formation of ore deposits and this metamorpliism. 

 The investigation occupied much time and was most laborious. 



It was known before these investigations were undertaken that the 

 deposition of cinnabar was probably still taking place at Sulphur Bank and 

 Steamboat Springs. It was of course necessary to make an effort to dis- 

 cover whether such was really the case, and, if so, under what conditions 

 the solution and precipitation of cinnabar and the accompanying minerals 

 occurred. The problems presented by this inquiry were far from being 

 simple or readily solved. 



Dr. W. H. Melville has had charge of my laboratory throughout the 

 period covered by these investigations. He has made all the analyses re- 



