CHAPTER XXXI. 
THE CARBONIFEROUS SYSTEM. 
A brief sketch of the various groups of strata which compose the great 
Carboniferous system has been given in the first volume of this Report. 
These will now be described somewhat more in detail, in order that our 
citizens may have a more exact and comprehensive knowledge of the 
composition and extent of this, the most important of the formations 
represented in the geology of our State. 
It is known to most persons that the name Carboniferous, or coal-bear- 
ing, was given to this group of rocks from the fact that they include in 
Kurope and America extensive deposits of mineral fuel, which not only 
constitute a marked feature in the formation, but have great economi- 
cal value, and have played a most important part in the development of 
our modern civilization. The name Carboniferous is, therefore, not ill- 
chosen, but it is liable to mislead, since the Deronian shales, in the Uni- 
ted States, hold quite as large a quantity of carbonaceous matter as is 
contained in our Coal Measures; and in China, India, and Western Amer- 
ica beds of coal occur in Mesozoic and Tertiary rocks which, in thickness 
and lateral extent, are not surpassed by our Carboniferous coal strata, 
while in these countries little or no coal occurs in rocks older than those 
mentioned. Hence, if geology had been first studied in China, a Carbon- 
iferous system would probably have been given a place in the geological 
column, but it would have been put at a higher level than it holds in 
our series. 
The Carboniferous system, known as such among our geologists, is 
usually regarded as one of the most distinctly defined of all the great 
groups of rocks, and yet in fact the lines which are now drawn to separate 
it from the Devonian below and the Permian above are as shadowy as 
any others that divide formations in the geological series. 
In England there has been much discussion as to where the lower 
limits of the Carboniferous system should be fixed, and there is still 
great difference of opinion as to how much of the Yellow sandstones of 
Ireland and the Upper Old Red Sandstone of Scotland should belong to 
the Devonian, and how much to the Carboniferous group. In our own 
country a similar difficulty has been encountered. The relations of the 
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