JOHN WESLEY POWELL I37 



1890. 



29. Work in petrography [and remarks on the classes and the 



study of rocks] . 



In United States Geological Survey, Tenth Annual Report, 

 Part I, pp. 43-52, Washington, 1890, royal 8°. 



Included in the paper-covered separates of the Director's 

 report. 



30. Conference on map publication. 



In United States Geological Survey, Tenth Annual Re- 

 port, Part I, pp. S6-79, pis. ii-v, Washington, 1S90, royal S° . 



Subheadings: the occasion for the conference ; the work 

 of the conference ; unit of publication ; nomenclature ; con- 

 ventional symbols for geologic maps ; conventional symbols 

 for geologic sections. 



1891. 



31. The new lake in the desert. By J. W. Powell. 



In Scribner's Magazine for October, 1891, vol. 10, pp. 

 463-468, New York, 1891, 8°. 



An explanation of the cause of the flooding of the Coahuila 

 Basin, Colorado Desert, southern California. 



1892. 



32. Our recent floods. By J. W. Powell, LL.D., Director of 



the United States Geological Survey. 



In North American Review for August, 1892, vol. 155, 

 pp. 149-159, New York, 1892, 8°. 



1893. 



33. The geologic map of the United States. By J. W. 



Powell, Washington, D. C. (Montreal meeting, Feb- 

 ruary, 1893.) 



In American Institute of Mining Engineers, Transactions, 

 vol. 21, pp. 877-887, New York, 1893, ^° - 



Read by Dr. C. W. Hayes, the author being unable to be 

 present. 



34. The mineral exhibits at Chicago. (Special.) [By J. W. 



Powell.] 



In British Trade Journal for November i, 1893, vol. 31, 

 pp. 520-522, London, 1893, foli*^- 



