Geology and Mineralogy. 399 



From artesian wells and borings, when the connection waters 

 are shut off by tubing, and when the pressure of the waters on 

 the thermometer was guarded against, as those made at Kentish 

 Town, Richmond, Sperenberg, Pregny and Ostend, give 5T9 

 feet per 1° F. In these wells the waters do not overflow. In 

 others which do overflow, and which should therefore give the 

 best results, as at Grenelle, Tours, Rochefort, Mondorff, Mitnden 

 and others, the mean afforded is 50 - 2 feet per 1° F. In the Sahara 

 Desert, the mean from 11 overflowing wells at depths of 200 to 

 400 feet gave 36 feet per 1° F. The author also considers the 

 variations resulting from difference of conductivity in rocks, but 

 makes no application of the subject. 



The mean thermic gradient deduced from all the observations 

 is 48 feet per 1° F. ; but this is considered only an approximation. 

 The question of change of rate downward also is considered but 

 the facts reviewed gave as regards this point no satisfactory 

 result. Professor Prestwich inquires in closing whether a gra- 

 dient of 45 feet per degree may not be nearer the true normal 

 than 48 feet. 



8. Notes on the Stratigraphy of California, by G. F. Becker. 

 U. S. Geol. Survey, No. 19. Washington, 1885. — In this paper, 

 Mr. Becker treats of the metamorphic rocks of the Coast Ranges 

 and their age; their identity with the Mariposa and Knoxville 

 beds, but non-conformity with the Chico beds; on the relations 

 of the Coast Ranges and the Sierra Nevada; and also on the 

 California Paleozoic rocks, and other points in California Geology. 



The age of the metamorphic rocks of the Coast Ranges is 

 shown to be near the limits of the Jurassic and Cretaceous. 

 They contain species of Aucella and other fossils near Knoxville, 

 identified by Dr. C. A. White, and the beds are hence named the 

 Knoxville group. Fossils occur also on Sulphur Creek in Colusa 

 Co., and at Mount Diablo, and according to White, near the New 

 Almaden Mine. The beds consist in part of serpentine which is 

 one of the alteration products, as described by Whitney and others. 

 The non-conformity with the Chico beds being established, the 

 period of Coast Range metamorphism must have been "before the 

 first of the Wallala beds were deposited and still longer before the 

 opening of the Chico period " — or " neither long before nor long 

 after the Neocomian." 



The Mariposa region is one of three along the western side of the 

 Sierra Nevada which affords fossils ; it is a narrow strip of coun- 

 try lying along the foothills from Mariposa to Nevada, which is 

 often known as the gold-belt proper — and its fossils, Aucella (A. 

 Piochii), Belemnites, etc., are regarded as showing identity with 

 the "Knoxville group." The rocks resemble those of the latter 

 group in kinds and in the prevalent silicification and serpentiniza- 

 tion. Dr. Becker observes that neither Dr. White nor himself could 

 find any reason for maintaining that the fossiliferous rocks were 

 not of the auriferous series ; or for dissenting from Prof. Whit- 

 ney's opinion that they form an integral portion of the modern 



