120 TRANSACTIONS OF THE [san. 20, 
lower down the cafion and none of the pits seen is in condition 
to give samples fit for analysis. But this bed should yield 
bituminous coal near the White Ash mine if the change toward 
the normal condition continue northward. An opening in Mad- 
rid is reported to have yielded some natural coke near its 
mouth. 
The thin coal beds above the middle of the interval between 
the principal beds are bituminous and show no evidence of 
change, even at two miles or more above the Lucas mine, where 
they yielded excellent coal for coke. These beds are badly cut 
by clay seams, the coal being replaced at times for several feet. 
Such complete replacement of the coal occurs very rarely in the 
White Ash and is unknown in the more southerly mines. 
CAUSE OF THE METAMORPHISM OF THE COAL. 
As already stated, both Dr. Newberry and the writer found 
the cause of metamorphosis in heat of eruptive rock in contact 
with the coal. The observations recorded in this paper seem to 
confirm that opinion, which, when first presented, was rather a 
suggestion than a conclusion, the facts being known imperfectly. 
The centre of eruption being in the Ortiz mountains, only two 
or three miles south from the area examined, the metamorphism 
ought to be more marked as that centre is approached. That is 
distinctly the condition, for at the most southerly pit showing 
the coal well, the anthracite is very hard and in part resembles 
the Rhode Island coal; but the change is less and less toward 
the north until normal coal is reached in the White Ash mine 
below Madrid. 
The gradation is equally clear in the coal of the Cook-White, 
but the small beds between the main seams appear to contradict 
the hypothesis, as they are decidedly bituminous at half a mile 
beyond the locality where the White Ash yields the hardest an- 
thracite. This condition, however, may be explained by the 
fact that the beds are not continuous; the clay seams would 
prevent the passage of heat from one portion to another. 
The conditions at several localities show that mere proximity 
to a mass of eruptive rock is insufficient to produce any mate- 
rial change in the coal. The lower plate is only 8 to 10 feet be- 
low the Waldo coal bed in the bore hole west from Coal canon, 
but, though 200 feet thick, it has had no appreciable effect upon 
the coal. The interval between the White Ash bed and the 
upper plate shows insignificant variations along the mesa front 
in Coal cafion, and the interval must be approximately the same 
in the newer portions of the White Ash mine; yet in the Lucas 
