Page:The Journal of geology (IA journalofgeology11893univers).pdf/258

mie coals on the western side of the great plains in New Mexico, Colorado and Wyoming can hardly have undergone any material change since the final burial; otherwise the strange variations in composition would be inexplicable, the difference in condition as to character of rocks and degree of disturbance being insufficient.

Twenty years ago the writer, while connected with the Ohio Survey, reached the conclusion that the marsh, from which sprang the several beds of the Upper Coal group, originated at the east; two years later he was led to assert that the coal beds were formed as fringes along the shore of the Appalachian basin. If this be the true doctrine, there should be found in northeastern Pennsylvania.

First. A vastly greater thickness of coal than in other portions of the basin.

Second. A greater advance in the conversion of vegetable matter into coal, owing to the longer period elapsing prior to entombment.

As to the first condition, there can be no doubt. A comparison of the several divisions of the Coal Measures as they appear in the several basins of the state illustrates it well; but such a comparison would be tedious here, and only the Lower Coal group of the Pennsylvania series is used (that lying between the Pottsville conglomerate below and the Mahoning sandstone above).

In the Anthracite Strip this group shows in the several fields, from south to north, as follows:

The thicknesses in the Bituminous basins are:

The thicknesses, as given for the Anthracite Strip, are those