COAL-FIELDS OF UNITED STATES. 303 
are those of Nova Scotia. These afford a bitumi- 
nous coal of good quality, and are situated in the 
regular coal measures. The quantity, of course, is 
very great, if not inexhaustible. 
Rhode Island Coal-fields. — These, though not 
extensive, are still worthy of notice. Those which 
'have been explored are situated chiefly in Ports- 
mouth, near the northern extremity of the state, 
and are contained in graywacke slate, and, conse- 
quently, are not in the regular measures. They be- 
gan to be worked about the beginning of the pres- 
ent century, when the bed wrought was fourteen 
feet wide. Six of these beds have been wrought, 
and more than thirty are said to exist in the vicin- 
ity. In 1820, fifteen men only were employed, who 
raised from ten to twenty chaldrons of coal per day, 
besides keeping the mine free from water. The 
bed is not horizontal, but forms an angle of about 
seventy-five degrees. In the year 1827, twenty men 
and five boys raised 2200 tons of coal, and an equal 
quantity of slack, which is very small coal and dust, 
and the coal sold at the mine for four dollars and 
fifty cents per ton, which was used for burning 
lime and bricks. Professor Hitchcock considers 
that the slate in which the coal occurs is closely 
alUed to primary rocks, because it contains as- 
bestos. 
Massachusetts Coal-fields. — -We have already 
alluded to the anthracite coal of Worcester, which 
occurs in mica slate. This is about seven feet thick ; 
but as it has been explored but a few feet, and the 
operations are now suspended, we shall pass it by 
without farther remark. 
Mansfield. — In the year 1835, explorations were 
commenced by the Massachusetts Mining Company, 
in the town of Mansfield, where a shaft was sunk in 
graywacke, and at a depth of 25 feet struck a bed of 
C09.1 five feet thick, and another one foot thick, sep- 
arated from the first by 10 inches of rock. Previous 
