373 Bibliographical Notice. 



Information obtained by the author on this occasion is brought to 

 bear on observations previously made, enabling Dr. Hayden to make, 

 in chapter xiii. of the memoir before us, " a condensed statement of 

 the leading geological discoveries up to the present time, and to 

 harmonize some of the conflicting opinions which may have been 

 advanced in regard to the age of the diiferent deposits in the west." 

 "Without careful reference to this third portion of the memoir, the 

 reader will misapprehend the author's views on several points, such 

 as the upheaval-era of the Rocky Mountains, the relations of the 

 lufrajurassic sandstones, the classification of the Tertiaries, &c. 



The memoir is illustrated by a few woodcut sections (seriously 

 limited on account of the cost of publication), and by a coloured 

 geological map, based on Lieut. Warren's survey. But this is a 

 mere sketch-map ; it does not include the Judith River (an important 

 locality), contains no indication of the "superficial deposits," and 

 mainly represents the determinations arrived at in 1857; and the 

 names of places have been chosen for insertion with little reference 

 to the routes of 1857-58 ; so that it proves but a poor help to the 

 careful student of this interesting memoir. 



In the "Historical Introduction" a short account is given of 

 former explorations made in the north-west territories. 



The rocks met with in the regions referred to, between the Missouri 

 and the Rocky Mountains, and on the western slopes of the Big Horn 

 and "Wind River ranges, are :— 



I. Granitic, metamorphic, and eruptive rocks in the axes of the 

 Rocky Mountains, the Black Hills, and Bear Peak (pp. 33 & 117, 

 &c.). Some lofty and extensive ranges consist of basaltic and other 

 volcanic rocks. 



II. Lower Silurian strata (referable to the Potsdam Sandstone), 

 consisting of siliceous limestone, micaceous sandstone, and calcareous 

 fossiliferous grit (with Lingula, Obolus, and Trilobites). This is 

 best seen in the Black Hills, where the upheaved strata engirdle the 

 metamorphic rocks. The author has found this fossiliferous primor- 

 dial sandstone along the eastern margin of the Big Horn range 

 (p. 120), and has recognized it in the Laramie Range ; and he thinks 

 that the sandstone and conglomerate of Stansbury Island and else- 

 where in the neighbourhood of the Great Salt Lake may be of the 

 same age, also the so-called "Old Red Sandstone" (Marcou) of the 

 Aztec Mountains in New Mexico. 



III. Carboniferous rocks, of great thickness, belonging to the 

 upper part of the series, and possessing but little coal, in North- 

 eastern Kansas and South-eastern Nebraska; whilst about 100 feet 

 of fossiliferous lim.estone, turned up around the Black Hills and 

 Bear Peak, and a variable group of sandy and calcareous strata, from 

 1000 to 1500 feet thick, with a few fossils, forming the western 

 outcrop of the great Carboniferous formation, where its edge is up- 

 raised along the Big Horn and the Laramie Mountains, and along 

 the Sweet-water and Wind River Mountains, represent perhaps both 

 the upper and lower members of the series (p. 121). Still further 

 north, the Carboniferous strata abound about the upper branches of 



