THE CARBONIFEROUS SYSTEM. 119 
rising on the coast opposite, at Bathurst, and rising at Prince Edward’s 
Island. (J. D. Dana.) According to Prof. G. H. Cook, the coast of New 
Jersey and Long Island is slowly sinking. On the coast of California I 
have observed several raised beaches marked by lines of marine shells— 
some of which still retain their colors—and rocks bored by Pholas. It is 
¢also plainly shown that the elevations have been local and unequal. 
There is, therefore, no inherent improbability in the view that the alter- 
nations of marine and terrestrial conditions, of which we find records in 
the Coal Measures, were produced by the sinking and rising of the bot- 
tom of the great geosynclinal trough of the Alleghany coal field. It is 
possible, however, that some of the influxes of the sea, of which we 
have record in the phenomena described, were produced by the breaking 
down of barriers by which the sea had been excluded. In such cases 
effects may have been produced similar to those that have been wit- 
nessed in the inundations of Holland. On the low coast of the Nether- 
lands the sea is carefully excluded by artificial embankments, and large 
areas have by this means been wrested from its grasp. On the marshy 
surface within the dykes by which the land is now protected beds of 
peat have grown. From time to time storms have broken over the bar- 
riers by which the sea is kept out, and it has rushed in, covering many 
square miles with its waters and the sediments they have transported. 
In such localities the sea has been again excluded by restoring the 
dykes, and peat is now dug in some of these districts, where it forms 
several strata separated by beds of gravel and.sand which mark succes- 
sive irruptions of the sea. In these peat beds, with the strata that di- 
vide them, we have a very close imitation of the phenomena presented 
by the beds of coal. This instance is cited as a possible, though not as 
a probable, explanation of the facts observed in our coal field. Some 
local submergences may have occurred in the manner suggested, but 
most of those recorded have been on too grand a scale, as it seems to me, 
to be the results of bursting of barriers without changes of level. 
The chemical processes which have been concerned in the formation 
of coal have been quite fully described in our former reports, and I shall 
give here only a brief review of the subject. Coal is now considered by 
all good chemists and geologists as of organic origin, and it may easily 
be demonstrated that it has been derived from the decomposition of 
vegetable tissue. It forms only one of a group of carbonaceous sub- 
stances which begins with woody fibre and ends with graphite. These 
are all derived from vegetable tissue in the changes which it undergoes 
when buried under water or earth. The different products of the pro- 
gressive change through which vegetable matter passes under such 
