ALLEGHENY AND CONEMATlGH IN ANTHRACITE FIELDS 221 



Messrs Ashburner, Hill, and Smith during their close study of the fields. 

 In much of the Southern field the interval between Mammoth and Skid- 

 more varies from 75 to 125 feet, but on the northern border, where that 

 field is in contact with the western Middle, survey sections and those by 

 Mr Lyman show : 



Feet. Feet. Feet. Feet 



Mammoth 



Interval 13 20 44 80 



Skidmore 



Interval . . 43 61 27 23 



Gamma 



these variations being in a distance of two miles and a half, the last at 

 Mahanoy tunnel, on the border between the fields. In the western 

 Middle the interval between Mammoth and Skidmore, west from Ma- 

 hanoy City, varies from 6 to 33 feet. In the eastern Middle one finds 

 this interval varying from 8 to 114 feet within a short distance, the Buck 

 Mountain at the latter locality being 300 feet below the Mammoth. In 

 the Hazleton basin, within a distance of 8 miles, one finds the interval, 

 Mammoth to Skidmore, increasing westwardly from 35 to 41, 110, and 

 200 feet, the workings being continuous. While farther north, in the 

 Black Creek basin, the interval between those beds varies from nothing 

 to 50 feet, that from Mammoth to Buck Mountain varies from 66 to 200 

 feet in the same area. Thus in Little Black Creek basin the Wharton 

 (Skidmore) is distinctly a split from the Mammoth, and the great de- 

 crease in interval to the Buck Mountain is such as to press the sug- 

 gestion that that lower bed also unites with the Mammoth- Wharton some- 

 where in the eroded area. 



The sections tell of great variability in coarseness of the material be- 

 tween the coal beds; limestone appears to be wanting everywhere; shale 

 and sandstone, the latter often conglomerate, fill the intervals. 



The material between Buck Mountain and Mammoth, in the eastern 

 part of the Southern field, is for the most part sandstone, with at times 

 immense beds of conglomerate; but near Pottsville slate predominates, 

 while southeast from Tremont there is no conglomerate and more than 

 half of the interval is filled with slate. Farther west the predominating 

 rock is sandstone, with little conglomerate, but at Lykens, in the northern 

 prong, conglomerate 48 feet thick is at 100 feet below the Mammoth. 

 Beds of conglomerate fill intervals between the Mammoth splits at a num- 

 ber of localities. In the western Middle coarse material, sandstone, and 

 conglomerate predominate east from the line of Mahanoy City; west 

 from that line there is much variation. At times conglomerates are on 

 the Buck Mountain and under the Mammoth, but near Shamokin the 



