94 
The American Geologist. 
February, 1896 
He also reminded the Society that similar brilliantly red sunsets fol¬ 
lowed the great eruption of Skapter Jokul in 1783. 
Prof. Hitchcock suggested that red glows due to aqueous vapor 
should not be confused with colors from volcanic dust, as the latter are 
prevailingly greenish; but in reply it was brought out that the colors 
are clue to diffraction, and that the reds may also be caused by fine par¬ 
ticles of mineral matter. 
A needed term in Petrography . L. V. Piksson, New Haven, Conn. 
Since the term crystal, when strictly used, means a body possessing not 
only a certain internal molecular structure, with definite physical prop¬ 
erties, but more especially an outward symmetrical form with plane 
faces, it is evident that there is no good term for the rounded or form¬ 
less masses in which minerals occur in rocks. Therefore, after consul¬ 
tation with Prof. E. S. Dana, the term anhedron (meaning without 
planes) is proposed for these formless masses which possess the internal 
structure of crystals; and such minerals may also be spoken of as having 
an anhedral development. 
In a brief discussion that followed, the term was on the whole well 
received, although the general feeling was strong against the introduc¬ 
tion of further new terms into the over-burdened nomenclature of pe¬ 
trography. 
The Cerillos coal field of New Mexico. John J. Stevenson, New 
"York City. (Read by title.) This paper describes a small jjortion of 
the area formerly known as the Placer coal field, south from the Rio 
Galisteo and about 25 or 30 miles south from Santa Fe, New Mexico. 
The only rocks within this area are Laramie and eruptive. The latter 
proceed from the laccolite known as the Placer or Ortiz mountains and 
occur in two sheets separated by about 400 feet of Laramie beds. These 
sheets, each about 200 feet thick, are intruded between the stratified 
rocks and follow their dip closely. The rock has been identified by Prof. 
Kemp as trachyte, but closely allied to andesite. The Ortiz or Placer 
mountains are about two miles from the most southerly locality visited. 
The column of Laramie exposed is not far from 1,000 feet thick and 
contains several coal beds of economic importance, only three of which 
are discussed in this paper. The highest bed, about 900 feet from the 
Lase of the column and known as the White Ash , has been opened at 
many places along the principal gorge, Coal canon. At the most north¬ 
erly mine, the White Ash, its coal is bituminous, containing 39 per cent, 
of volatile combustible, but at the Lucas mine, not more than 3,000 feet 
farther up the canon, it is anthracite with only 1 per cent, of volatile. 
The interval between these mines contains for the most part coal so 
crushed as to be practically unmarketable ; but, as shown in one level 
of the White Ash mine, the transition from soft to anthracite coal is 
Gradual. Farther up the canon, toward the Ortiz mountains, the coal 
becomes harder and at one opening resembles the Rhode Island anthra¬ 
cite. 
