IRON MANUFACTURE. 447 
numbered consecutively from the base of the series, and their relation- 
ships may be readily understood by reference to the general section of 
the Coal Measures in Ohio. 
The Coal Measures are composed of alternating strata of coal, iron 
ore, limestone, sandstone, fire-clay and shale. And thus, beside con- 
taining large supplies of coal, they include some valuable ores of iron, 
building material, limestone, quite generally distributed and sufficient 
to supply all the demands of iron works for flux and lime, and not least 
the fire-clays from which are made ordinary fire-brick, glazed ware, etc. 
In some localities a peculiar variety of fire-clay occurs, whichis made 
into fire-bricks, which are unexcelled for durability and refractoriness 
by the celebrated Mt. Savage brick, of Maryland, or any other made in 
the country. The aggregate thickness of the coal seams in the Lower 
and Barren Measures is about 40 feet, and in the Upper Coal Measures 
20, or approximately 50 feet in all, though as the Coal Measures are 
only of this maximum thickness in a small portion of the State, the 
available thickness of coal in the State is much less, probably not over 
one-half of this. 
The lower group of coals contains by far the most important part 
of the mineral wealth of the Coal Measures in Ohio. They include all 
the most valuable furnace fuels and the only deposits of iron ore of any 
note in the State. At least three quarters of the coal area in the State 
have them as the surface rocks, while they are also more or less deeply 
buried under the Upper Coal Measures, which occupy the remainder of 
the coal area. The Geological Survey have recorded in this group six 
workable seams of general distribution, beside several others, which 
are locally thick and valuable. And their relation and thickness may 
be seen by referring to the geological section of the Coal Measures. 
THE MANUFACTURE OF IRON IN OHIO. 
The history of the iron industry in Ohio begins with the erection 
of a blast furnace at Poland, Mahoning county, a few miles southeast 
of Youngstown. This furnace was founded by Messrs. Montgomery, 
Clendenin & McKay, in 1806, and began to make iron in 1808. It 
was a small charcoal furnace, 30 feet in height and 7 feet across the 
boshes, cold blast and blown by water-power, producing only about 
two tons of iron per day. The iron made was principally cast 
directly from the furnace into various forms, such as pots, kettles, 
g 
