J. P. Kimball—Grahamite in the Huasteca, Mexico, 279 
caused by the gradual elevation, or periodic oscillations of level, 
of the Cordilleras during the Tertiary period and afterwards, 
and which phenomena, as I have elsewhere noted, are likewise 
strongly marked in northern Mexico. 
The area over which my route lay, is occupied by argillaceous 
sandstone, calcareous in places, whose foldings seem, generally 
speaking, to correspond with the present configuration of the 
surface, the whole of which, however, has been subjected to a 
ey powerful erosion. One of the most remarkable evidences, 
of the gradual character of the elevation of the Cordilleras 
in the lower latitudes, and of the fluvial character of their ero- 
that they are more logically referred to the Tertiary. These 
shales are important as the seat of the grahamite deposits in the 
Vicinity of Tempoal, and probably throughout the much larger 
¢ cageesea including, at least, the middle portion 
» the Capadero basin, or so much of it as lies between the 
uejutla Mountains on the west and the Alacranes hills on the 
st The region thus defined corresponds to the so-called 
Coal-field of the Huasteca,” the coal, however, as I judge from 
* This Journal, xlviii, 1869, p. 381. 
