February 15, 1906] 



NA TURE 



377 



once more an outburst of basaltic lava filled up the canyons 

 to a depth of at least 500 feet. Still in their old courses, 

 but displaced from their channels, the streams had again 

 to commence re-excavation. At the present time they have 

 cut through more than 500 feet of the hard basalt wilhout 

 reaching its bottom. The two periods of canyon cutting 

 probably belong to the " Sierran " epoch of Le Conte. 

 Hot springs, desert conditions, glaciation, and the in- 



fluence of domestic animals upon river erosion forn 

 subjects of notes. The illustrations are beautiful, 

 helpful to the text. 



The region about the northern limit of the Cascade 

 Range was traversed by Messrs. G. O. Smith ami F. C. 

 Calkins (4) in a rapid reconnaissance. The older rocks 

 encountered are grouped together as pre-Cretaceous, com- 

 prising (1) old-looking schists along the 

 Columbia River and lower Okanogan 

 Valley ; (2) supposed Carboniferous 

 sediments with volcanics in the more 

 northern part of the Okanogan Valley ; 

 (3) strata similar to the last mentioned 

 exposed in the base of the upper Skagit 

 River ; (4) some old sediments and a 

 great volcanic mass near Hamilton ; 

 and (5) a great assemblage of strata 

 ranging from Palaeozoic to Jurassic 

 lving to the west and north of Mt. 

 Baker. 



An extensive development of the Cre- 

 taceous is indicated from the Hozomeen 

 Range on the west to the Similkameen 

 Range on the east; the name 

 " Pasayten formation " is proposed for 

 this in place of Prof. Russell's term 

 Similkameen. Sandstones and shales 

 predominate ; contemporaneous igneous 

 roil,.-, appear to be absent. Tertiary 

 sediments occupy a much smaller area 

 than do the Cretaceous, but volcanic 

 rocks, presumably of this age, are of 

 some importance. Later formations are 

 represented by glacial and river gravels, 

 and by the andesitic lavas of Mt. 

 Baker.' 



As compared with their immense importance in the 

 southern Cascades, the part played by volcanic rocks in 

 the boundary section appears very subordinate. Plutonic 

 rocks are greatly developed, the prevailing type being a 

 " grano-diorite." The volcanic rocks range from soda- 

 rhyolite, dacite, acid and basic andesites, to basalt. The 

 dyke rocks include a soda-syenite from south of Bighorn 

 Peak, and a diorite (?) in which apatite occurs in broad, 



1894. VOL. 73] 



irregular plates as one of the last products of crystallisation. 

 The authors conclude that volcanic and plutonic rocks alike 

 may have been derived from a homogeneous magma, low 

 in alkalies, with soda predominating over potash ; hence 

 they may belong to the same province as the rocks of the 

 southern Cascades and the Sierra Nevada. 



Dr. Dale has written a short account of the strati- 

 graphy of a strip of the Hudson Valley (51 between the 

 Hudson River on the west and the 

 Rensselaer Plateau and the Taconic 

 Range on the east. The difficulties in 

 the way of delimiting the age and re- 

 lations of the several formations are the 

 rarity and bad preservation of the 

 fossils, the repeated minor overfolding, 

 and the prevalence of Glacial drift. 

 An excellent map accompanies the 

 paper on the scale of 1 inch to the 

 mile ; fossil localities and good outcrops 

 are clearly indicated by a system of 

 coloured spots — a plan worthy of imita- 

 tion. 



The formations represented are Lower 

 Cambrian, Beekmantown shale with 

 Dictyonema and Clonagraptus, the 

 Hudson shale and Hudson schist (Ordo- 

 virian = Trenton), and the Silurian 

 Rensselaer I irit = Oneida, Medina. 



Three crustal movements are recog- 

 nised in the area : — (a) at the close of 

 the Lower Cambrian, Upper and Middle 

 Cambrian are missing; (b) the Taconic 

 or Green Mountain movement which 

 folded the Ordovician beds ; (c) a post- 

 Devonian or Carboniferous movement 

 which folded the Silurian Grit of the 

 Rensselaer Plateau. Minor oscillations 

 are indicated by conglomerates which occur in the Lower 

 Cambrian, in the Hudson shale, and in the Rensselaer Grit. 

 Although onlv ten years had elapsed since Cross and 

 Penrose made a careful study of the Cripple Creek district, 

 the people of Colorado asked for a re-survey on account 

 of the great development of underground working in the 

 interval ; this re-survev has been undertaken bv Messrs. 



Fig. 



Canyon, Crooked River, Crook County, showing basalt of inner canyon in 

 tact with stratified beds of outer can) on. (Bulletin 252.) 



Lindgren and Ransome, who have now issued a report of 

 progress (6) in advance of the laboratory examinations. 



The oldest rocks in the district are the muscovite and 

 fibrolite schists ; these are closely associated with fine- 

 grained granitic gneiss. Both gneiss and schist are cut 

 bv a reddish granite. A second type of granite is the 

 coarsely porphyritic Tikes Peak type. As a result of the 

 recent work, the views of Cross upon the rocks erupted 



NO. 



