CERRILLOS COAL FIELD OF NEW MEXICO. 527 



Above Madrid fragments on the old dumps show that the coal is anthracite. A 

 pit at the lower end of Madrid, almost midway between the Cunningham and 

 White-ash mines, shows a tender coal which resembles that from Pocahontas, in 

 Virginia. Analysis shows that it contains about 30 per cent of volatile, which is 

 about what should be expected if its changes are similar to those of the White-ash. 



The Waldo bed is not reached in the upper part of Coal canyon, but it has been 

 mined extensively further down. The only interest it has here is its existence in 

 the bore-hole west from Coal canyon, where it is not more than 10 feet above the 

 lower plate of trachyte, and shows no evidence of any metamorphism whatever. 



Long ago Newberry and afterward Stevenson regarded the coal as metamorphosed 

 by heat from a great dike of eruptive rock following the northerl}^ side of the Placer 

 (now Ortiz) mountains. This, which then was but a suggestion, is sufficientlj^ 

 clear as an explanation now. As the center of eruption was in the Ortiz moun- 

 tains, the metamorphism should be most notable near those mountains. That is 

 distinctly the condition, for at the most southerly point showing the White-ash 

 bed well the anthracite is very hard, 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 Cook- White bed, but the small bed between the 

 main seams appears to contradict the hypothesis, as it is decidedly bituminous at 

 half a mile above the pit where the White-ash bed yields the hardest anthracite 

 observed. This condition is easily explained by the fact that the small bed is 

 broken by clay seams several feet wide, which sometimes cut out all of the coal ; 

 these seams would prevent the passage of heat from one portion to another. 



The conditions at several localities show that mere proximity to the mass of 

 eruptive rock was insufficient to produce change. The lower plate of trachyte is 

 but 10 feet below the Waldo coal bed in the bore-hole west from Coal canyon, but, 

 though 200 feet thick, it had no appreciable effect upon the coal. The interval 

 between the White-ash bed and the upper plate of trachyte shows insignificant 

 variations along Coal canyon, and it must be approximately the same in the newer 

 parts of the AVhite-ash mine, yet in the Lucas mine and at all localities south from 

 it the coal is anthracite, whereas at all points north from it to the border of the 

 eruptive rock one Unds only transition coal. It seems clear that direct contact is 

 necessary to produce change. 



Professor J. F. Kemp describes the eruptive rock as a trachyte closely allied to 

 andesite. Its outflow then was early, possibly at the time of the Laramide eleva- 

 tion, when great outpourings of andesite occurred in Colorado, Utah, Wyoming 

 and Montana. The coal was completely formed prior to this elevation, prior to any 

 disturbance, there being not only no evidence of pulpiness, but every evidence that 

 the coal was thoroughly hard. It was crushed into minute fragments, slickensided 

 like the Utica shales of Franklin county, Pennsylvania, or laminated and rolled 

 into leaves like the Vespertine coals of southwestern Virginia. The process of con- 

 version was complete before disturbance, not merely in the lowest beds, but also in 

 the White-ash bed at nearly 900 feet above the bottom of the Laramie. 



The scientific program was declared finished. Vice-President Charles 

 H. Hitchcock offered the following resolution, which was unanimously 

 adopted : 



^'Resolved, That the sincere thanks of the Geological Society of America are 

 hereby tendered to the officers of the University of Pennsylvania for their kindness 



