REVIEWS 441 



for whom the work was written. There is a hint that the scientific 

 results will be specially treated in some later work. The scientist will, 

 however, find this work rich in phenomena of the highest interest, not 

 less in the illustrations than in the text. No work on the great white 

 north has ever been so amply and so accurately illustrated as this. 

 The 800 photographic illustrations tell their own story. Lieutenant 

 Peary was as fortunate as he was industrious in making an unassailable 

 photographic record of his explorations. Neither storms, dangers, 

 nor stress of circumstances seem to have stopped the work of his 

 ever-present kodak. The mechanical execution of the half-tones, 

 while in the main fair, yet leaves something to be desired. Their 

 extreme value would have warranted the use of the best available paper 

 and of the utmost skill in printing. Their execution is sufficiently 

 good, however, to lend an inestimable value and interest to the text. 



T. C. C. 



United States Geologic Atlas, Folio 41, Sonora, California. 1897. 



The folio consists of seven pages of text signed by H. W. Turner 

 and F. L. Ransome, geologists, a topographic map of the district, an 

 historical geology sheet, an economic geology sheet, and a structure 

 section sheet. 



The quadrangle represented in this folio lies between the parallels 

 of 37 30' and 38 north latitude, and meridians of 120 and 120 

 30' west longitude. It comprises a portion of the western slope of 

 the central Sierra Nevada, chiefly in the foothill region. The quad- 

 rangle covers portions of Tuolumne and Mariposa counties, including, 

 also, corners of the valley counties of Stanislaus and Merced. The 

 area is drained chiefly by the Tuolumne and Merced rivers. 



The formations are divided into two main groups : The bedrock 

 series, and the superjacent series. The bedrock series is composed 

 of Juratrias and Palaeozoic sediments with interbedded lavas and tuffs, 

 and a series of old igneous rocks, chiefly quartz-diorites, serpentine 

 derived from peridotite, and porphyries. The Juratrias rocks are 

 chiefly clay-slates with some sandstone, and are called the Mariposa 

 formation, since the characteristic Jurassic fossils of the formation 

 were first found in Mariposa county. The Mariposa formation is 

 represented by three distinct belts of slates, the most eastern belt of 

 which is remarkable as containing in part the gold-bearing veins of 



