Geology and Mineralogy. 75 
the composition consequently must be considered somewhat 
doubtful. The mineral is named from Dr. A. von Groddeck, 
Director of the Bergakadamie at Clausthal.—Z. Kryst., viii, 343, 
1883. 
11. Mineral Resources of the United States; by ALBERT 
and revised as additional facts are collected. 
12. Lehrbuch der Mineralogie ; von Dr. Gustav TscHERMAK, 
IT Lieferung, pp. 369-589, Vienna, 1884 (Alfred Hélder).—The 
two preceding parts of Professor Tschermak’s Mineralogy.have 
already been noticed in this Journal (III, xxiii, p. 68; xxiv, p. 
Pp 
way of figures. h 
class of students for whom it has been prepared. 
