Taking the area of this field to be 750 square miles-a most probable estimate-we may classify the contents as household coal, steam coal, or those employed in steam-engine boilers, and coking coal, employed for making coke and gas.
"Lectures on Popular and Scientific Subjects"
John Sutherland Sinclair, Earl of Caithness
Of household coal there is only 96 square miles out of the total 750, all the remainder being steam or coking and gas coal.
"Lectures on Popular and Scientific Subjects"
John Sutherland Sinclair, Earl of Caithness
The region of Connellsville contains almost 150 square miles underlaid with coal that has a particular heat value when submitted to the process known as coking.
"The Age of Big Business Volume 39 in The Chronicles of America Series"
Burton J. Hendrick