12 ANNUAL EEPORT OF THE 



An apparatus for imitating geyser eruption was added to the 

 laboratory. 



The following papers were published : — 



A Microsclerometer for determining the Hardness of Minerals, Am. 

 Jonr. Sci., Vol. IV., 1897. Same in German, Groth's Zeitschrift fur 

 Krystallographie, Bd. XXIX., Heft 3. 



Some Conditions affecting Ge3'ser Eruption. Am. Jour. Sci., Vol. 

 V., May, 1898. 



An Occurrence of Acid Pegmatite in Diabase. Amcr. Geologist, 

 Vol. XXI., April, 1898. 



In press : — 



Death Gulch, a Natural Bear-Trap. Appleton's Pop. Sci. Monthly. 



In the summers of 1897 and 1898, Dr. Jaggar has been engaged 

 in work on the U. S. Geological Survey of the Yellowstone Park 

 Timber Reservation under Mr. Arnold Hague, and the mining dis- 

 trict of the Black Hills under Mr. S. F. Emmons. In the spring 

 of 1898, a special investigation on " The Hardness of Nephrite 

 and Jadeite " was completed, to be a chapter in a monograph on 

 " Jade," prepared by Mr. Heber Bishop of New York. Dr. Jaggar 

 has in preparation a Handbook of Experimental Geology. 



