Barbour and Torrey — Microscopic /Structure of Oolite. 249 



Figs. 5 and 6. — Micro-sections of Siliceous Oolite from Pennsylvania, magnified 

 10 diameters. 



The following is an analysis of the siliceous oolite : 



Siliceous Oolite. 



Silica 95-83 



Oxide of aluminium ) 9 _„ 



Oxide of iron ) 



Lime 1 '93 



Magnesia trace 



100-69 

 Specific gravity 2*63 



Single granule from Pennsylvania 

 Siliceous Oolite. 



Silica 99-99 



Iron 00-01 



100-00 



Single granule from the Iowa 

 River Oolite. 



Silica .. . . 2-54 



Iron trace 



Calcium carbonate.. 97-44 



99-98 



These interesting specimens of siliceous oolite were sent us 

 by Mr. George K. Wieland of State College, Center Co., Pa. 

 Two miles west of this place there are three or four square 

 miles of light sandy soil, mostly uncleared, hence called the 

 " Barrens," where this oolite, associated with flint, occurs 

 scattered about in the form of surface bowlders weighing as 

 much as 400 pounds. The fact that these masses of siliceous 

 oolite are stained with iron oxide, and that they occur in an 

 isolated spot, may account for their having escaped more gen- 

 eral notice hitherto. It is said to occur also about fifteen miles 

 northwest of College Centre. 



Iowa College, Department of Geology and Chemistry, 

 April 2, 1890. 



