-3- 
trachyte, while the broken edges of the beds are fre¬ 
quently, but abruptly, pressed up, as if by the upward 
or lateral pressure of the rising mass. He was able to 
make many additional observations on the geology of the 
San Juan region, and secured much valuable material for 
the coloring of the final map. 
TT He states that the northern limit of ancient 
cliff-builders in Colorado and Eastern Utah is hardly 
above latitude 37°45’. fT 
