A 
302 GEOLOGY OF OHIO. 
ments. In Paris the introduction of coal meta similar fate; it was 
condemned, and its use forbidden ; it was accused of polluting the air, 
producing disease of the chest and lungs, and even impairing the beauty 
and delicacy of the complexion of ladies. 
The manner of mining in these primeval times was necessarily 
rude. At points where a seam of coal exposed itself along its line of 
outcrop, the alluvial cover was stripped off, and the coal quarried in 
open day, as beds of sandstone for building purposes are now quarried 
out. When necessity required an opening to be made unaer cover, the 
seam was followed along its line of strike, in order that the waters of 
the mine might discharge themselves by gravitation. The double- 
headed pick, still the main weayjon of the miner, has been in use from 
the earliest times. A thousand years ago this mining tool was as per- 
fect as it is to-day, and the miner of the ninth century could produce 
as much coal from his working place as the miner of the nineteenth 
century. 
When increasing demand for coal made it necessary to open mines 
below water level, the seam was opened either by following it along its 
line of dip, or by sinking a shallow shaft near the outcrop.. The horse- 
gin, still to be found in some mining districts, was employed for hoisting 
coal. The machinery used for discharging the waters of the mine con- 
sisted of ox-skins and barrels ; then chain-pumps were applied, operated 
by horse-power, or by wind-mills. Frequently day levels were cut at 
great labor and expense to a lower level, or adit, so that the water 
might flow to day. In locating a shaft, a primary object was to find a 
place near the opening, so that a day level might be cut to rid the mine 
of water. In laying out the workings, small pillars were left to support 
the roof, which were abandoned after the room workings were finished. 
When shaft mining was commenced, fire-damp, that dreaded scourge 
of coal miners, was met. Until the discovery of the safety-lamp by 
Sir Humphry Davy, the miner possessed no means of detecting the 
presence of this gas in his subterranean workshop, except by creeping 
forward inch by inch, with his candle held in one hand, screening the 
flame with the two fore-fingers of the other, and fixing his eye intently 
upon the light. When he reached the fire-damp, the flame of his candle 
began to elongate and to assume a color of grayish blue; before the gas 
exploded, the top of the flame changed to a pure fine blue and gave off 
minute luminous sparks. The miner could still retreat before explosion 
