Show heavy coal producers the concentration or of the anthracite industry of 0 pennsylvania into strong and relatively few te units Is show riby the fact that in 1911 dearly 75 to per cent ot of the mines were producers ot of more lore than tons each cadi and that all but 3 per cent of 0 the total production vas from this group of 0 mines according to the geological survey the anthracite mines exclusively in the first class those producing over oer 00 tons each yielded per cent ot of the total output and the mines included lit in this class had an asiago production of 0 tons each in 1910 there were anthracite mines in the ton class and their average pio production was tons each in ia 1909 mines had an ae production of 0 tong bac each h |