REVIEWS 95 



It is concluded that if methane were the sole explosive gas, only local 

 explosions near the face of the coal could result. Coal dust is present, 

 however, in large quantities and can under proper conditions become 

 explosive. The chief restraining agent on dust explosion is dampness, and 

 the presence of a high proportion of non-combustible shale dust. A great 

 reduction of the moisture in mine atmospheres results from the incoming 

 of cold air at the beginning of winter, and it is observed that most of the 

 great explosions have been at that time. 



It is a general belief that old dust exposed for a long time to the air 

 is more dangerous than fresh dust, but the author shows by experiment 

 that this belief is erroneous, and that fresh dust is the. more explosive. 



E. R. L. 



Reconnaissance of the Book Cliffs Coal Field between Grand River, 



Colorado, and Sunny side, Utah. By G. B. Richardson. U.S. 



Geol. Surv. Bulletin 371. 



The field forms a part of the south rim of the Uinta basin, around whose 



margin the outcrops of coal-bearing rocks can be traced for more than 



five hundred miles. Three formations of Cretaceous rocks are mapped: 



the Dakota sandstone lying unconformably on Morrison beds, the Mancos 



shale of Colorado and Montana age, and the Mesaverde formation which 



is overlain unconformably by Wasatch beds. The Mesaverde is partly 



marine and partly non-marine, the marine part showing close similarity to 



the upper Mancos shale and the non-marine to the Laramie. The age 



is placed as pre-Laramie, the Laramie epoch being supposedly represented 



by the unconformity above. 



Coal of good quality occurs in the lower part of the Mesaverde forma- 

 tion in some localities. Several beds are present, but no single bed has 

 been traced for more than a few miles. The coal of the region is little 



developed. 



E. R. L. 



Cenozoic Mammal Horizons of Western North America. By Henry 



Fairfield Osborn, with Faunal Lists of the Tertiary Mammalia 



of the West by William Diller Matthew. U.S. Geol. Surv. 



Bulletin 361. 



This report is primarily a correlation of the mammal-bearing horizons 



of the Cenozoic with one another and with those of Europe, with a brief 



characterization of each horizon. In the Tertiary, six faunal phases are 



