148 
AGE CHARACTERISTICS OF COALS 
roof, in which case the stream was probably contemporaneous 
with the bog; but not infrequently the channel-way was excavated 
after the roof had been formed. The conditions are common¬ 
places in modern deposits. 
Cretacic coals are usually so far advanced in conversion as to 
give little information respecting the plants of which they were 
formed. Knowledge of the flora of the period-is mainly derived 
from fragmentary materials found in the associated rocks. 
It has been transported; and represents mostly the upland vegeta¬ 
tion, telling nothing about the swamp plants. In the United 
States and Canada Cretacic coals are often rich in resins, in¬ 
dicating that conifers entered largely into their composition; such 
wood as has been recognized seems to confirm this conclusion. 
Cycads were abundant locally during the deposition of the 
Kootenai beds, but conifers and dicotyledons were predominant 
during the Late Cretacic times while ferns and lycopods appear 
to have been subordinate. European information upon this sub¬ 
ject is scant. Wood, clearly recognizable, is present in the Late 
Cretacic coals of the Loewenberg region; but in the Griinbach 
coal no structure is shown, although the stems and branches re¬ 
tain their form. The Wealden coals of Hanover contain abun¬ 
dance of conifers, cycads, lycopods and ferns. The plant re¬ 
mains must be very distinct there. Dunker thinks that the “black 
coal” of that region was derived from lycopods and ferns ex¬ 
clusively because they are the only forms found in it; the lignitic 
coal is largely of conifer origin, since the stems occuring in it 
resemble those of Pinus. 
Consideration of the chemical relations of the Cretacic coals 
has to be taken in connection with those of the older coals. Cer¬ 
tain features are of special interest. Like the Tertic coals and 
some peats these coals are resinous in many districts. Cannel 
co^ is present at several horizons. Carbon content is higher than 
in the Tertic coals; but progressive enrichment with increasing 
age is less marked. In the Fox Hills coals the extremes of carbon 
are 73 and 83 per cent.; in Pierre, 71 and 84; in the Benton, 77 
and 83; and in the Kootenai, 75 and 85. 'No note is taken of the 
metamorphosed coals; and anthracite is present at several horizons. 
No ultimate analyses of the Laramie coals are available, and there 
are very few of the Kootenai. Variations are small compared 
with those of the Tertic coals. Among the Cretacic, as in the 
