866 THE JOURNAL OF GEOLOGY. 



the replacement of feldspar by epidote, the host apparently exerts no orient- 

 ing influence on the epidote as is often stated to be the case. The epidote is 

 often arranged in zones and sometimes is concentrated in a rim within the 

 feldspar individual. The explanation of this is sought in variations of chem- 

 ical composition within concentric zones of a single feldspar crystal. The 

 alteration of feldspar to muscovite is much less frequent than to epidote. 



The staurolitic mica schist separating the areas represents a sedimentary 

 deposit more ancient than the granites and probably owes its highly crystal- 

 line character to contact metamorphism. 



The study of granite soils with the aid of the miner's pan showed the pres- 

 ence of a number of minerals not noticed in the thin sections. 



C. H. G. 



Erosion in the Hydrographic Basin of the Arkansas River above Little 

 Rock. By J. C. Branner. (An. Rep. Geol. Surv. of Ark., 1891, 

 Vol. II.) 



The observations on the erosion in the Arkansas River basin, while not as 

 exhaustive as the State Geologist desired them, owing to limited resources 

 at his command, they nevertheless furnish a valuable addition to the literature 

 on this subject. The physical and chemical character of the sediment is 

 described, and a number of analyses given. The tabulated results of the 

 amount of material carried in suspension and the amount carried in solution 

 for each month in the year are given. 



More than twenty-one million tons are carried in suspension and nearly seven 

 million tons, or nearly a third as much in solution. In November during very 

 low water, the amount in solution was six times that in suspension, while in 

 May and June during high water, the amount in suspension was more than 

 five times that in solution. The results are compared in part with those of 

 other rivers. 



Other papers in the same volume are Elevations, Magnetic Observations, 

 and Bibliography, by J. C. Branner ; Mollusca, by F. A. Sampson ; Myriopoda, 

 by C. H. Bollman ; Fishes, by S. E. Meek ; The Geology of Benton County, 

 by F. W. Simonds and T. C. Hopkins ; and Geology of Dallas County, by C. 

 E. Siebenthal. 



The Dallas County report is accompanied by a topographic map, and 

 contains a discussion of the topography and the general geologic features ; 

 but the chief point of interest is the description of the potter's clays. It con- 

 tains numerous analyses, a list of the occurrences of the clay deposits and a 

 history of the pottery industry in the county. The pottery clays of other 

 parts of the state, along with the other valuable clays of the state, will be 

 described in a forthcoming volume on clays by the State Geologist. 



T. C. H. 



