THE SANDROCK.
This is the upper workable seam in the anthracite mea sures; but it is generally considered too small for attention at present, though we believe it has been worked as the South Salem. It ranges from 2 to 4 feet, and lies from 100 to 150 feet above the Salem, or M. N is worthy of note simply as the upper workable seam, but otherwise it is insignificant, and scarcely deserves a name and location among the many magnificent beds which we have illustrated : inclusive, however, it constitutes the fifteenth seam.
To all of these, except A and C, we have attached the most popular name, and have frequently given the local names as applied in different districts. We may here note an omission, however, in case of the Mammoth, which was known generally during the early development of the Coalcastle or Mine Hill basin as the " Daniel," after the first operator, Mr. Francis Daniel, now of Yatesville, in the Mahanoy valley.
We have given names to the two lower nameless beds A and C, as Alpha and Gamma. These, however, are unimportant seams, and no one will be concerned about their names. The liberty we have taken in giving them some definite title is simply for convenience.
The names and thickness of the respective seams as we have now classi fied them, in the Pottsville district, we give in the accompanying table.
Thus the minimum thickness of the coal-seams would be about 60 feet, the average thickness 123, as given in figure 74, and the maximum 205 feet. The thickness of the measures would stand thus, inclusive of the coal :—minimum, 880 ; average, 1750 ; maximum, 2380. These figures merely represent the distances from the lower to the upper coal-seam, or from A to N. The unproductive measures above N may vary from 300 to 1000 feet, according to location and situation.