ecedes the crushing, let us first consider it as
it was projected and carried on by him.

Perhaps quarrying would be a better term than mining in this case, as
Edison's plan was to approach the rock and tear it down bodily. The
faith that "moves mountains" had a new opportunity. In work of this
nature it had been customary, as above stated, to depend upon a high
explosive, such as dynamite, to shatter and break the ore to lumps
of one hundred pounds or less. This, however, he deemed to be a most
uneconomical process, for energy stored as heat units in dynamite at
$260 per ton was much more expensive than that of calories in a ton of
coal at $3 per ton. Hence, he believed that only the minimum of work
should be done with the costly explosive; and, therefore, planned to use
dynamite merely to dislodge great masses of rock, and depended upon the
steam-shovel, operated by coal under the boiler, to displace, handle,
and remove the rock in detail. This was the plan that was subsequently
put into practice in the great works at Edison, New Jersey. A series of
three-inch holes twenty feet deep were drilled eight feet apart, about
twelve feet back of the ore-bank, and into these were inserted dynamite
cartridges. The blast would dislodge thirty to thirty-five thousand tons
of rock, which was scooped up by great steam-shovels and loaded on to
skips carried by a line of cars on a narrow-gauge railroad running
to and from the crushing mill. Here the material was automatically
delivered to the giant rolls. The problem included handling and crushing
the "run of the mine," without selection. The steam-shovel did not
discriminate, but picked up handily single pieces weighing five or six
tons and loaded them on the skips with quantities of smaller lumps.
When the skips arrived at the giant rolls, their contents were dumped
automatically into a superimposed hopper. The rolls were well named, for
with ear-splitting noise they broke up in a few seconds the great pieces
of rock tossed in from the skips.

It is not easy to appreciate to the full the daring exemplified in these
great crushing rolls, or rather "rock-crackers," without having watched
them in operation delivering their "solar-plexus" blows. It was only
as one might stand in their vicinity and hear the thunderous roar
accompanying the smashing and rending of the massive rocks as they
disappeared from view that the mind was overwhelmed with a sense of the
magnificent proportions o