556 WESTERN COAL MEASURES AND INDIANA COAL. 
In the Block-coal zone of the Indiana coal field, there are as 
many as eight seams of non-caking coal, four of which are of 
good workable thickness over a portion of the field. These are I, 
G, F and A, which, together, have a maximum thickness of fifteen 
feet, and by including the other four seams, we have six feet more, 
making a total of twenty-one feet of block coal. 
The superior excellence of the block coal for smelting, and 
working iron and steel, in all the varied departments of their man- 
ufacture, has been fully established by practical tests. Pig iron 
made with this coal is in every respect equal to charcoal iron 
` made from the same ores; it is a soft gray iron of a highly erys- 
talline structure, contains a large percentage of combined carbon, 
with but a mere trace of sulphur and phosphorus ; properties which 
render it admirably adapted to the manufacture of Bessemer steel. 
For steam and household purposes it likewise has an unrivalled 
reputation. It burns under boilers with a full and uniform flame 
that spreads evenly over the exposed surface, thus securing a more 
uniform expansion of the boiler plates and greater freedom from 
leaks that are so common when caking coals are used. No clink- 
ers are formed, and owing to its freedom from sulphur it has but 
little detrimental effect upon the boilers, grates or fire boxes. 
The western zone of coals in Indiana comprises by far the 
greatest area of measures, being somewhat over six thousand 
square miles, and contains three or more very thick beds of coal, 
besides a number that are too thin for working. Its eastern boun- 
dary, which is formed by the zone of block coal, is irregular in 
outline, and with my present knowledge of the geology of the 
country, it cannot be well defined. It is evident, however, that 
the block coal beds, as we go west, are changed in character and 
pass into caking coal. The lower members thin out, and are no 
longer of workable thickness, even before reaching the Wabash 
river. Of this we have abundant proof by the three deep bores 
at Terre Haute. 
These bores commence about forty feet above low water of the 
Wabash river, and after passing a few feet of alluvium deposit, 
were in strata of gravel, sand and hard pan, peculiar to the drift 
epoch, for a depth of about one hundred and fifty feet, and though 
they penetrate the Silurian rocks, the records show that but five 
seams of coal were passed; only the top one being of workable 
thickness, while the lowest is but two hundred and eer hem 
and three-quarters feet below the surface. 
