conclusions. 69 



Relation of increasing Thickness of Coal to decreasing Volatile 



IN -Pennsylvania. 



Under such conditions one should expect the amount of volatile com- 

 bustible matter to show marked decrease in the beds as they approach 

 the old shorelines. This decrease is shown by the analyses. In the 

 anthracite strip the ratios are as follows : 



Cumberland basin"^ 4.47 to 4.78 



Broad Top 3.26 to 4.64 



Southern anthracite : 



Southeast prong (the longer) 4.63 to 12.40 



Southwest prong 8.91 to 11.30 



Main field 11.64 to 23.27 



Western Middle 19.87 to 24.00 



Eastern Middle 25.53 to 30.35 



Northern 19.33 to 19.92t 



Similar variations are found along the trend in the several bituminous 

 basins. Thus in the first, the Clarion coal-bed shows from 2.94 to 4.84 

 near the Maryland line, but 5.48 to 6.09 in Lycoming county and 7.07 

 to 10.28 in Sullivan; the Brookville varies from 2.14. in Somerset to 4.13 

 and 6.93 in Sullivan. In the second basin, the Upper Freeport is 2.26 

 and 2.85 near the Maryland border, but becomes 3.96 to 4.48 in Lyco- 

 ming ; and the Clarion changes from 2.25 in Indiana to 3.88 in Tioga. 

 But in the third basin it is not easy to make such comparisons, for the 

 lower coals are buried deeply at the south and the higher coals extend 

 but a little way northward from the Ohio and Conemaugh rivers. At 

 the same time, it is clear that the variation becomes much less in this 

 broad basin than it is in the basins nearer the anthracite region, which 

 is precisely what we should exi)ect. There is, however, a distinct de- 

 crease of volatile northward, as shown by the analyses of the Upper 

 Freeport in Beaver, Armstrong and Clarion counties. The result of 

 comparison is to show that the decrease of volatile is found along a line 

 following the trend northward and along the line eastward to which 

 Rogers referred. 



Conclusions. 



The conditions, then, are — 



First. A decided increase in thickness of the coal series eastward or, 

 better, northeastward toward the anthracite region and a less marked 

 increase northward in the bituminous basins. 



* Analyses of the Pittsburg coal-bed ouly are accessible. 



+ These results of analyses are by Mr A. S. McCreath, except those from the southeast prong of 

 the Southern field, which are taken from R. C. Taylor's Reports on Coal Lands of the Dauphin and 

 Susquehanna Coal Company, 184U. Mr McCreath's analyses, for the most part, are in his second 

 report, already quoted so often, and in the Annual Report for 1885. 



