February 13, 1913] 



NATURE 



659 



T 



One Hundred New Double Stars. — Dr. Aitken 

 continues his publication of newly discovered double 

 stars in No. 223 of the Licli Observatory Bulletins. 

 The present list contains the data for 100 objects, all 

 measured with the 36-in. refractor, and brings the 

 total now discovered up to 2500 ; of these only seven- 

 teen have distances greater than 5-0", while in 1847 

 the components were separated by less than 2-0". 

 The original programme included the examination of 

 all stars down to the ninth magnitude, given in the 

 B.D., from the north pole to —22° declination, and 

 95 per cent, of the area to — 14° has now been sur- 

 veyed ; of the remaining area, —14° to —22°, only 

 about one-quarter remains to be examined. 



CONTRIBUTIONS TO AMERICAN 

 ECONOMIC GEOLOGY.^ 



""HE State of Texas consists mainly of plains of 

 Cretaceous and Cainozoic rocks which slope 

 gradually eastward to the Gulf of Mexico. They are 

 interrupted to the north-west of the city of Austin by 

 an outcrop of pre-Cambrian rocks composed of 

 granite, gneiss, and schist, and of some early 

 Pateozoic sediments, including Cambrian and Ordo- 

 vician. These older rocks of Texas have been de- 

 scribed in a bulletin by Mr. Paige, who has proved 

 that they have been faulted up into their present posi- 

 tion. These old rocks contain some iron ores, of 

 which the Survey during its work in the region dis- 

 covered thirty-two occurrences. Only three are suffi- 

 ciently large to be of economic importance, and their 

 value is still unproved. The ores are masses of mag- 

 netite ; they occur in the schists and usually along 

 the contact with the granites or in bands of rock 

 crushed between parallel faults. The iron was origin- 

 ally deposited in marine sediments, and has been 

 concentrated in consequence of the intrusion of the 

 granites and diabases and of the faulting. The 

 author, in concluding his discussion, quotes a passage 

 from Van Hise attributing the origin of many ores 

 to the materials of igneous rocks, and he inserts iron 

 in the list given by Van Hise; but the case of iron 

 is so different from the others that this addition is 

 scarcely justified. 



The existence of a tar spring associated with some 

 hot springs near Lander, in Fremont Count}', Wyom- 

 ing, was sufficient indication of petroleum to justify 

 the search. A report by Mr. E. G. Woodruff de- 

 scribes the geology of the district and the evidence 

 as to its supplies of oil. The neighbourhood consists 

 of a series of rocks ranging from the Carboniferous 

 to Eocene, and including a long series of the Meso- 

 zoic. There are two oil-bearing horizons, of which 

 the most prolific is the Embar formation, belonging 

 to the Carboniferous ; there is a smaller supply in the 

 Upper Cretaceous. The thirteen existing wells yield 

 a supply of 330 barrels a day. The field is one of 

 those in which the productive positions occur along an 

 anticlinal axis. 



The Salt Creek oilfield in Natrona County, also in 



1 •■ Mineral Resource'^ of the Uano-IInrnel Ri-gion, Texas, with .w 

 Accounl of the Pre-Cambnan Geolog)-." By .S Paige. Bulletin 450, 

 U .S. Oeological Survev, Washington, igii. Pp. 10,+v pIates+22 tigs. 



"The Lander and Salt Creek Oil Fields. Wyoming." The Lander Oil 

 Field. Fremont C .nnty. By E. O. WoodrufT. The S.alt Creek Oil Field, 

 Natrona County. By C. H. Wegemann Bulletin 451, U.S. Geological 

 Survey. Washington, igti. Pp. 87 + xii plates+i tig. 



" A Geologir Reconnaissance in South-eastern Seward Peninsula and the 

 Norton Bay— Nulat.) Region, Alaska." By P. S. Sroith and H. M. F..akin. 

 Bulletin 449, U.S. Geological Survey, Washington. 1911. Pp. 146+xiii 

 plates4-,5 ligs. 



"Geoogvand Mineral Rrsources of the Nizina District, Alaska ' By 

 F H. MofBt and S. R. Capps. Bulletin 448. U.S. Geological Survey, 

 Washington, 1911. Pp. iii+xii plates+ii figs. 



•' Com ributions to Economic Geology." (Shi»rt Paoers and Preliminary 

 Reports, IQ09.) P.trt ii.. Mineral Fuels. [M. R. Campbell, Geologist in 

 Charge!. Bulletin 431, Wasbinslon, 1911. Pp. 2;4 + .xii plates4-4 figs. 



NO. 2259, VOL. 90] 



Wyoming, is described by Mr. C. H. Wegemann. 

 The country consists of Cretaceous rocks, lying be- 

 tween some Eocene beds and one which may be 

 Jurassic. The oil-bearing horizons are the Upper 

 Cretaceous Shannon "Sands," some 8 ft. of sand- 

 stone saturated with oil. The oil from a lower bed, 

 the Wall Creek "Sand," rises in intermittent flows 

 like a geyser, and Mr. Wegemann attributes the 

 ascents to the same cause as geyser eruptions. A 

 small quantity of oil also comes from a sandstone at 

 the base of the Cretaceous series, which is regarded 

 as possibly the equivalent of the Dakota Sandstone. 

 This oil is associated with water, which in this case 

 is fresh. Mr. Wegemann briefly discusses the origin 

 of the oil ; he regards it as derived from organic 

 matter, and especially fossil fish in the adjacent 

 shales, from which it passed into the sandstones. 

 Mr. Wegemann regards this view as supported by the 

 presence of sulphur in the oil. 



The Seward Peninsula, the most western part of 

 the mainland of America, projects into the Bering Sea 

 between Norton Sound and Kotzebue Sound. A re- 

 connaissance geological survey has been in progress 

 for ten years, and has been completed by the work 

 of Messrs. P. S. Smith and H. M. Eakin on two 

 sheets, which include the country extending from the 

 north of Norton Bay eastward to the Lower Yukon 

 Valley. The country is geologically complex. It has 

 a base of Archsean rocks covered by a varied series of 

 Palaeozoic sediments. In Middle Mesozoic times the 

 region was occupied by land which was submerged in 

 the Cretaceous, though the evidence as to the exact 

 horizon of the marine Cretaceous beds is still in- 

 definite. Great post-Cretaceous earth movements, 

 accompanied by some igneous intrusions, folded and 

 faulted all the lower rocks; as some of the dykes 

 have been faulted, the movements continued later, but 

 the post-Cretaceous faults had no direct influence on 

 the topography. The country was subsequently dis- 

 sected by river erosion. The country was never 

 covered bv an ice sheet, in spite of its high northern 

 latitude and its proximity to the sea ; but the authors 

 discovered traces of small glaciers in some of the 

 valleys. The country has shared in the post-Glacial 

 oscillations which are so conspicuous along the 

 Alaskan coasts. The economic minerals of this dis- 

 trict include alluvial gold, silver, lead, and copper, 

 and some Cretaceous coal. 



The chief copper mines of Alaska are situated 

 among the Wrangell Mountains at the head of the 

 Copper River. Some of the most promising ore bodies 

 occui; in the valley of the Chitistone River, a little to 

 the west of the Canadian frontier. The rocks of this 

 district are all Mesozoic, and include the Upper Trias- 

 sic Chitistone Limestone and Macarthy Shales. The 

 age of the Kennicott formation is still somewhat 

 doubtful ; it has been often referred to the Lower 

 Cretaceous, but in the view of the authors is probably 

 Upper Jurassic. Unlike the Seward Peninsula, the 

 country has a comparatively simple geological 

 sequence, and has been strongly glaciated. It shared 

 in the great Cretaceous uplift, which led to its dis- 

 section bv stream erosion. The valleys were moulded 

 by ice, which, according to the authors, not only gave 

 them their trough-shaped form, but deepened them 

 bv from looo to i.^oo ft., an estimate based on the 

 height of the hanging valleys. The dissection of the 

 country was aided by two series of faults which inter- 

 sect at right angles and divide the country into blocks, 

 some of which have been lifted and others lowered. 

 The countrv was thus disturbed by displacements 

 which, though small, had an important indirect effect. 

 One exceptional geographical feature is described by 

 Moffit and Capps as "rock glaciers." They consist 



