AGE CHARACTERISTICS OF COALS 
145 
Belief that Cretacic deposits were practically continuous 
throughout this area is of comparatively recent date. The preva¬ 
lent conception until within a little more than 20 years was that 
the Rocky Mountains had existed during Cretacic time. 
Certain chemical features are characteristic of the Cretacic 
coals. No substance resembling the pyropissite of Sachsen has 
been mentioned by any observer, the only allied material being that 
seen by Bunker in the Hanover region, which he thought might 
be hatchettin. Resin of one sort or another occurs commonly. 
By some authors it is termed Bernstein, retinite, walchovite, or 
simply resin. It occurs in grains or lumps, some of the latter 
being several inches in size from the lower Quander coals of 
Bohemia and Moravia. At one locality in Hungary it is so 
abundant as to give the local name to a coal seam. There is 
much in New Zealand. In North America resins are character¬ 
istic features of coals in the Laramie, the Fox Hills and the 
Pierre formations, as well as those of the Benton beds. The 
color is given from honey-yellow to dark-yellow, and according 
to Thiessen it is rather darker in the Fox Hills coals of northern 
Colorado than in the Eocene coals of the Dakotas. Resins ap¬ 
pear to be wanting in bituminous coals of high grade; at least no 
note is made anywhere respecting their existence in such coals. 
One who reads reports covering extensive areas is liable to 
believe that caprice has determined the distribution of coal. The 
presence of coal at one locality gives no assurance that it will be 
found at the same horizon in others, for great barren spaces 
exist between productive areas, so that individual seams appear 
to have small areal extent; apparently the total area on which 
coal was accumulating at any one time was a compartively insig¬ 
nificant part of the whole. There is, however, an evident relation 
between the occurrence of coal seams and the prevailing character 
of the sediments, which would justify the assertion that in one 
locality coal may be present and that in another it is almost 
certain to be absent. The descriptions seem to prove that coal 
seams accumulate only under conditions such as mark great 
river, or coastal, plains, where intervals of relatively rapid subsi¬ 
dence were followed by others during which subsidence was 
slow; finer materials were deposited on the coarser and coal ac¬ 
cumulation began. But where the deposits were fine, such as those 
