THE LOWER COAL MEASURES. 153 
used to but small extent in foundries, and find their main applications 
in heating purposes where quality is not essential. The use of these 
waste products in this way is an important step in the line of fuel 
economy, a topic which our coal producers are just beginning to con- 
_ sider. 
The seams used for coking are especially the Freeport coals and 
the Pittsburgh. No successful manufacture now exists in any other 
seam, in fact, except in. the two cases already noted of the Lower and 
Middle Kittanning coals, at Leetonia and Hammondsville, respectively. 
5. The requisites for a good milling coal are quick combustion, 
with plenty of flame, together with as much purity as can be secured. 
The Brush Creek coal, the Freeport coals, and the Kittanning coals 
furnish the chief supply. Each of these several seams does good service 
at some point or other in its development. 
The Salineville Strip seam (Brush Creek coal), the Steubenville 
Shaft seam (Lower Freeport), and the Leetonia coal (Lower Kittan- 
ning) all enjoy excellent reputation as milling coals. The Pittsburgh 
and the Upper Freeport seams are also considerably used. The Block 
coal of the Mahoning Valley is highly esteemed for this use wherever 
the price at which it can be afforded allows it to be used. 
6. For gas making, our native supply is not drawn upon to any 
great extent outside of the State boundaries. Within these limits 
several seams are used with a fair degree of acceptance. The Hocking 
Valley coal furnishes by far the largest supply for this purpose. The 
inferior quality of the coke produced puts them all at a disadvantage 
when compared with the Pittsburgh coal. 
PREPARATION OF CoAL FOR MARKET. 
Almost all Ohio coal is sorted and cleaned by a process called 
screening, before it is brought into market. All that is used for 
domestic purposes is treated in this way, also all that is used in iron 
making. Until quite recently, all railroad fuel has also been screened. 
A large proportion of it is still prepared in this way, but there is a 
growing tendency on the part of railroad companies to either use the 
coal as it comes from the miner’s pick, which is technically known as 
the “run of mine,” or else to throw together two or more of the several 
grades of coal that have been sold separately hitherto. 
There are two grades of coal supplied by almost all mines, and 
