COAL BEDS. 79 



agriculture this method may be deemed inapplicable. Therefore the only 

 use which can be made of these bogs is for plantations of cranberries. In 

 the method of cultivation which is commonly employed with that plant, 

 several thousand acres of these drainable lands, especially the areas in the 

 eastern parts of the basin, are well fitted to this mode of tillage. 



COALS. 



The coal beds of the Carboniferous series afford the most important 

 economic resources of the basin. As is indicated in the portions of this 

 memoir which have been prepared by Messrs. Foerste and Woodworth, 

 these beds are probably limited to the lower half or shale-bearing portions 

 of the great section. So far as is known, no deposits of any importance 

 exist in the zone of the upper conglomerates. The exhibition of these coals 

 is the clearest in the region where they have been most extensively mined, 

 on the western side of the northern part of Aquidneck Island. At this point 

 they are seen dipping to the eastward near the surface at an average angle 

 of about 30°, with a diminishing slope as the workings penetrate toward 

 the center of the syncline. In this section at least two coal beds occur, the 

 lowest of which is about 2,000 feet below the base of the upper conglom- 

 erates, and the highest within perhaps 1,000 feet of that line. 



In the western and northern parts of the basin the same or other coal 

 beds occur. Of these, the deposits in or near Pawtucket and at Cranston 

 are the best known. The bed at Pawtucket — there seems to be but one — 

 lies apparently several thousand feet farther down in the great section than 

 the beds of Aquidneck. It is likely that this bed is continued southwardly 

 near the margin of the basin to near its southern end, and that the various 

 exposures which have from time to time been made along this line lie upon 

 it. It is also probable that the coal along the northern part of that border, 

 as far as Wrentham, is of the same or a closely related stratum. 



The bed of coal in Cranston may most reasonably be regarded as 

 equivalent to one of those in the Aquidneck section. Its position in relation 

 to the upper conglomerates, however, can not be ascertained with any 

 certainty; so its place must be left in doubt. 



The coal beds which were at one time worked in Mansfield are in such 

 a position that they can not be safely placed in reference to the other known 

 deposits. The relation of the beds to one another and to the immediate 



