GEOLOGICAL SURVEY OF FORTIETH PARALLEL. 303 



Mr. King chose as his geological assistants the brothers J. D. and 

 Arnold Hague, and S. F. Emmons, all of whom had received good 

 training in the geological survey of California, and proved competent 

 and congenial co-laborers with him. Specialists were also engaged to 

 study the materials collected in other departments of natural science ; 

 the fossils being placed in the hands of Mr. F. B. Meek, and, after his 

 death, in those of Professor James Hall and Mr. R. P. Whitfield. The 

 botanist of the survey was Mr. Sereno Watson, and the ornithologist 

 Mr. Robert Ridgway, while a special investigation of the volcanic 

 rocks collected was made by Professor Ferdinand Zirkel, the distin- 

 guished lithologist of Leipsic. The topographical work of the survey 

 was, during the greater part of its continuance, in charge of Mr. J. T. 

 Gardner, now director of the Topographical Survey of the State of 

 New York. 



The report of the " Survey of the Fortieth Parallel," as now pub- 

 lished, consists of six volumes quarto. Of these the first issued (1870) 

 was Vol. III. of the series, entitled " Mining Industry," and devoted 

 to a description and discussion of the important mines and mining dis- 

 tricts embraced in the territory studied. About half of the volume is 

 taken up with a detailed description of the Comstock lode the most 

 productive deposit of gold and silver yet discovered and of the 

 methods of exploitation followed in the different mines located upon 

 it, by Mr. King and J. D. Hague. It also contains chapters by Mr. 

 Arnold Hague on the " Chemistry of the Washoe Silver Process," and 

 on the " Geology of the White Pine Mining District " ; the " Geology 

 of the Toyabe Range," by S. F. Emmons ; and on the " Geological 

 Distribution of Mining Districts," and the " Green River Coal Basin," 

 by Mr. King. This volume is accompanied by an atlas of maps, plans, 

 and sections, which at the time of its appearance was by far the most 

 beautiful work of its kind published in this country. 



It is greatly to be regretted that the review of the mining industry 

 of the country bordering the Pacific Railroad, so admirably begun in 

 this volume, could not have been continued through the life of the 

 survey, and have been presented to the public at its close. Since the 

 publication of this discussion of the Comstock lode, the most important 

 chapters in its history have been enacted, and it is a pity they should 

 not also have been written. When Mr. King closed his examination 

 the workings had reached a depth of a little more than 1,000 feet, and 

 the maximum temperature, (of water at bottom) was about 108 Fahr.; 

 and now the depth of 2,500 feet has been reached, tbe temperature of 

 the water at the bottom is 160, and facts have been obtained which 

 indicate that the limits of the successful working of the lode will be 

 determined by temperature and these limits soon be reached. 



The Sutro Tunnel has also been constructed and all its geological 

 revelations made since the appearance of Vol. HI. The great bubbles 

 of the White Pine and the Emma mines have since swollen and burst, 



