82 GEOLOGY OF THE NAEEAGANSETT BASIN. 



information as to the extent and thickness of these beds can not be had 

 without extensive and systematic exploration with the drill, but some results 

 could be obtained by well-planned superficial excavations. 



It should be noted that, owing to the thickness of the barren upper 

 part of the section of the rocks in the basin, nearly one-fourth of its area 

 has the coal-bearing beds so deeply buried that they are below the level 

 where they could be mined; in much of the area the estimated depth 

 exceeds 10,000 feet. Moreover, nearly another fourth of this area is occu- 

 pied by the waters of the sea, so that it may be regarded as impracticable 

 to explore the underlying rocks. The remaining half is fairly open to 

 inquiry provided there should be found a market for coal of the peculiar 

 quality which it affords, at a cost which would be imposed by its physical 

 and chemical conditions. These we will now note : 



CHARACTERISTICS OF THE COALS. 



Wherever found, the coal of this basin has certain characteristics which 

 distinctly separate it from any other fossil fuel that has been mined in 

 this country. The material is everywhere extremely anthracitic, often 

 ranging in appearance toward graphite. It is usually much penetrated by 

 veins of varied and rather complicated nature. It is high in ash, the pro- 

 portion commonly being 10 per cent, and often attaining to near twice that 

 amount, This ash contains in most instances a singularly large amount of 

 lime, which causes the cinders to smelt and thus clog the grate bars of a 

 stove or boiler furnace. As is shown by the accompanying analysis, the 

 percentage of fixed carbon is abnormally high, yet an extended trial of the 

 coal in producing steam showed that the value for this purpose was but 72 

 per cent of that of Lackawanna coal. The reason for this disproportion 

 may have been in part the lack of adaptation of the fire boxes to the 

 character of the fuel, which evidently needs a very strong draft, and the 

 fusible nature of the slag, which makes it difficult to keep the grate bars 

 clean. It is possible, however, that a portion of the carbon is in some 

 special chemical state which hinders its ready combination with oxygen, 

 perhaps in the condition of the supposed graphitic acid of Graham. 



