WHITE] THICKNESS OF POTTSVILLE IN SOUTHERN FIELD. 857 



out this portion of Sharp Mountain, IT miles in lengih, for the reason 

 that no coals were expected to occur there; (3) that nearly the entire 

 formation, including both groups of the Lykens coals, lies south of 

 the general crest of the mountain; (4) that the discovery, especially in 

 the Lower Lykens division, of several Lykens coals, one or more of 

 which appears to be of good quality and of workable or nearly work- 

 able thickness at every point ^ at which a moderately thorough search 

 has ))ecn made along the opposite side of the basin and along Short 

 Mountain, offers every assurance of the presence of some of the coals 

 on the south side of the basin, though the steep or nearh^ vertical 

 position of the beds bespeaks a poorer condition and less eas}' exploita- 

 tion of the coals. It is, however, within the range of probability that, 

 should the consumption of anthracite continue at nearly the present 

 rate, the demand for the Lykens red-ash coals, which are more highly 

 appreciated for domestic purposes, will exhaust the richer and more 

 favorably situated and profitably mined deposits, some of which are 

 already far toward exhaustion, and cause the exploitation of Lykens 

 coal in regions now regarded as wholly unprolitable; in which case the 

 Lykens coals of Sharp and Stony mountains, though so often crushed, 

 may enter into competition with the thinner coals of the Pottsville 

 formation in other portions of the anthracite fields. 



THICK^S^ESS OF THE FOBJIATIOX I]S^ THE SOUTHERN 

 AINTTHKACITE FIELD. 



In the discussion of the lower limits of the Pottsville formation 

 attention was especially called (p. 831) to the great variations in the 

 measurements of the section in the Southern Anthracite field, due to 

 the indefiniteness of the method in use and the elements of personal 

 opinion and preference consequently involved. As was then remarked, 

 the method of fixing the boundary at the top of the highest bed of 

 typical red shale or sandstone, which has been followed in the meas- 

 urements hitherto given in this report, is only the application in the 

 anthracite region of the custom in vogue in the geologic work of the 

 l)ituminous basins of the State. The unsatisfactory features of this 

 method, which have already been pointed out in the Southern Anthra- 

 cite field, are appreciated in advance.^ It is admittedly arbitrary and 

 variable; yet in its application it not only assures an identical horizon 

 over considerable distances, but it is definite in each exposure, and 

 effectually disposes of the personal variations resulting from the choice 

 of an individual horizon throughout a series representing a gradual 



• Dull and Hoff lands north of Rattling Run Gap ami drifts north of Rausch Gap, mine sheets xxv 

 and xxiii, respectively. 



-Concerning the variability of the horizon of the uppermost bed of red shale, Smith (Summary Final 

 Report, Vol. Ill, Pt. I, p. 1921) remarks as fijllows : "In the Southern field these transition beds have, 

 in places, a thickne.>is of 500 to GOO feet. The transition beds and the lower beds of XII also exhibit 

 decided variations in the materials composing them. At times heavy conglomerates predominate, 

 with but few sandstones and shales, or again the whole series may be composed of coarse saTidstone.s 

 and of shales, with the green and reddish tinge running high in tlie formation, making it difficult, 



