Oris'in of the Caves — Kraus 
171 
forms in the roof, which correspond to the uneven places 
in the floor. 
We may, therefore, sum up as follows : The change 
of anhydrite to gypsum has given rise to the folding which 
is quite prevalent in this section, the abundant water supply 
has caused the solution of large amounts of gypsum, where- 
by a partial collapse of the overlying strata resulted, leav- 
ing an open space between the strata, which still remain 
folded and those which settled. No doubt this explanation 
will also apply to the formation of some of the other caves. 
In the "Crystal" cave it is difficult to make observations as 
to the relation of the roof to the floor on account of the 
large number of well developed celestite crystals, which 
occur attached on all sides of the cave. In Kindt's cave the 
conditions are somewhat similar to those in Perry's. As 
yet I have not been able to examine Danssa's cave, but in- 
asmuch as this cave is in very close proximity to the Perry 
cave, the above explanation, no doubt, also applies to it. 
Mineralogical Laboratory, University of Michii:;an. 
THE GEOLOGICAL AND TOPOGRAPHICAL FEATURES OF THE 
CITY OF MONTEREY, NUEVO LEON, MEXICO, AND ITS 
VICINITY. 
Ernest Wittmann, Monterey, Mex. 
Sir: — While recently in the City of Monterey, Mexico, I was 
greatly struck by the singular geological formation of the canyons 
and mountain ranges in the vicinity. The lofty and slender peaks 
of blue limestone rising abruptly from the level campania, with 
almost vertical stratifications which give them the appearance ot 
fluted columns are truly impressive, not to say weird-looking, differ- 
ing so greatly from anything to be seen out of New Spain. Ono 
fully recognizes the force of Humboldt's words: 
"There is scarcely another part of our globe where the moun- 
