The name Carboniferous was given in the early part of the last century, when it was supposed that every geological system was characterized by the presence of some peculiar kind of rock. We now know that this conception is erroneous, and that workable coal seams have been formed in all the periods since the Carboniferous. It still remains true, however, that the latter contains much the most important share of the world's supply of mineral fuel, upon which the whole fabric of modern industrial civilization is founded. The great economic importance of the coal measures has caused them to be most carefully surveyed in all civilized lands, a process greatly assisted by the innumerable shafts and borings which penetrate these rocks. One result of this gigantic work is, that the history and life of the Carboniferous are better known than those of any other Palaeozoic period, though our knowledge is still very far from complete.

The Carboniferous rocks are displayed in very different aspects or facies in the various parts of the continent and even in contiguous regions. New York no longer gives the standard scale, for that state has very little that is newer than the Devonian. For the eastern part of the country the sequence of strata in Pennsylvania serves as the scale of reference, while a very different one is needed for the Mississippi valley. In the Rocky Mountain region, again, the character of deposition deviated markedly from what occurred in the East, and all over the far West the Carboniferous is almost entirely marine, without coal. Even in this region, however, the distinction between the Lower and Upper Carboniferous may be drawn. The following table gives r 609 the succession in England, Pennsylvania, and the middle West, Illinois, Missouri, Iowa, etc.

Carboniferous System