Personal and Scientific News. 395 
its hall will be a revelation to those persons who have not 
visited the Museum during this period. 
Professor W. C. Brogger, of the University of Chris- 
tiania, lectured at the University of Chicago on Ma}- 14th 
and 15th. His subject was "The genetic classification of ig- 
neous rocks". On the 15th Prof. T. C Chamberlin gave a 
dinner in honor of Prof. Brogger. Those who attended the 
lectures included the special students in geology at the Uni- 
versity of Chicago, a few from Northwestern University, and 
the following geologists: 
C. P. Berkey, University of Minnesota. 
T. C. Chamberlin, University of Chicago. 
A. R. Crook, Northwestern University. 
O. C. Parrington, Field Columbian Museum. 
U. S. Grant, Northwestern University. 
W. F. E. Gurley, University of Chicago. 
W. H. Hobbs, University of Wisconsin. 
J. P. Iddings, University of Chicago. 
A. C. Lane, State Geologist of Michigan. 
H. W. Nichols, Field Columbian Museum. 
C. W. Rolfe, University of Illinois. 
J. A. Udden, Augustana College. 
C. R. Van Hise, University of Wisconsin. 
Stuart Weller, University of Chicago. 
L. G. Westgate, Evanston High School. 
At The April Meeting of the New York Academy 
OF Sciences, Section of Geology and Mineralogy, doctor 
R. Ellsworth Call presented "Some Preliminary Notes on 
Crystal Growths in Mammoth Cave." He first gave a brief 
resume of the geology of the vicinity of Mammoth cr.ve. The 
strata making the geologic section are nearly horizontal, and 
all the rocks forming the cavern are of sub-Carboniferousage. 
The region of the cavern is capped with sandstones of the 
Chester group 500 feet thick, beneath which are oolitic and 
other limestones, in which the cavern is excavated to a thick- 
ness of over 350 feet. The drainage level of the cavern is de- 
termined by the present level of Green river. Five different 
levels have existed during geologic time. No gypsiferous 
strata are known in the region. The overlying sandstone is 
usually quite ferruginous, but no pyrite occurs. Secondary 
crystallization has occurred in many of the stalactites causing 
them to simulate the fibrous appearance sometimes as- 
sumed by arragonite. The stalactites of recent origin 
almost all have a downward-projecting tree-root as their 
origin of fixation, or are beneath sink-holes. The chief 
objects of mineralogical interests are the gypsum crystals 
which cover the sides and ceilings of certain avenues in 
the cavern, in the upper of the five levels only, and not 
in any levels now occupied by streams. These crys- 
tals are sometimes curiously and remarkably contorted and 
the terminations of the crystal masses are often recurved in a 
