150 GEOLOGY OF OHIO. 
cent. of ash. The products of some of the choicest mines will fall to 2 
per cent., or even to 14 per cent., but there is no district that can live 
up to this rate. The average ash of the best coals that supply the State 
at present exceeds 5 per cent. | 
Users oF Onto COoALs. 
A few general statements as to the chief uses of Ohio coals will be 
given here, in order that the detailed statements that follow may be 
seen in their proper light. 
The following list shows their more important applications : 
Household use.—Grates, stoves, furnaces. 
Steam production. {1 stationary engines, 
Tron smelting coal. 
Coke manufacture. 
Rolling mill fuel. 
Gas making. 
Ca EX bo Fg 
1. For household use there is no fixed and common standard. 
Widely separated varieties are used with apparently equal acceptance 
in different sections of the State. The rich, cementing coals of the 
Pittsburgh district have long been the chief supply of the Ohio Valley, 
and here they hold their ground against all competitors. 
The open-burning coals of the Mahoning and Upper Tuscarawas 
Valleys are the standard fuels of Northern Ohio. Through Central 
Ohio, several distinct varieties have each the decided preference in as 
many distinct fields. The most accessible coal will generally be used 
by each section, and acquaintance with the character of this particular 
fuel will often lead to its being retained, even when competing coals of 
intrinsically higher, though different quality, reach the market. 
There are, however, some general considerations by which the 
degree of adaptability of our several coals to domestic use can be determ- 
ined. Tor this, as indeed for all other uses, low percentages of ash and 
sulphur (pyrites) are desirable, as it is to these elements that the produc- 
tion of “clinker” is due. It must also be free from slate and “ bone.” 
Furthermore, the coal must ignite easily, and still must hold the fire at 
least moderately well. A fairly high percentage of carbon is of course 
necessary. The less smoke and soot it makes in burning the better. 
In addition to these points, its physical properties must also recommend 
