REVIEWS 307 



Throughout the state the principal supplies are found in recent 

 deposits in beds and terraces of the larger streams. Exceptions are 

 found, but in general those counties crossed by drainage lines leading 

 from the drift area have important deposits. The Mississippi River 

 floodplain supplies the eastern tier of counties with much sand and some 

 gravel, but similar deposits of the Missouri are more often charged with 

 silt. In the area reached by the Wisconsin ice sheet, extensive deposits 

 of sand and gravel are available in kames and eskers in addition to recent 

 stream deposits. 



Stone suitable for road and concrete work is limited to the eastern 

 part of the state. In the west neither the argillaceous limestones of 

 Pennsylvanian age nor the loosely cemented Cretaceous sandstones 

 made good road materials. In the east and northeast, limestones are 

 available, ranging in age from Ordovician to Mississippian. In many 

 localities stone is not available on account of the heavy overburden of 

 drift. Counties along the Mississippi River and its larger tributaries 

 furnish the most favorable quarry sites. 



A valuable feature of this report is found in the tables. They are 

 compiled from data furnished by experiments on various properties 

 important in road materials. Standard tests on cementing value, 

 toughness, and hardness show a wide range of values. Good cementing 

 properties may be associated with poor wearing properties or vice versa. 

 Inferior hardness may decrease the value of materials excellent in other 

 respects. These results show the necessity of thorough testing before 



final selection. 



W. B. W. 



Geology of the Pitchblende Ores of Colorado. By Edson S. Bastin. 

 Prof. Paper, U.S. Geol. Survey, No. 90-A. Shorter Con- 

 tributions to General Geology, March 17, 1914. Pp. 5, 

 pis. 2. 

 The sources of uranium in the United States are given and the 

 principal foreign occurrences of pitchblende (a complex uranate of 

 variable composition) briefly described. Quartz Hill, which is near 

 Central City, Gilpin County, Colorado, is "not only the one important 

 locality in the United States where pitchblende occurs in mineral veins 

 but one of the few in the world." 



The oldest rocks of the area are included in the pre-Cambrian Idaho 

 formation, which is mainly a quartz-mica schist. Pre-Cambrian granites 



