In average hard-rock mining, from three to five of these holes are drilled in a space four-by-six feet in area.
A stick of dynamite is exploded by inserting in one end of the stick a high-power detonating cap which will deliver a twenty-pound blow per X--whatever that means.

From three- to six-X caps are used in ordinary mining.

Three-X caps sometimes fail to explode a stick of dynamite.

A six-X cap, delivering a one-hundred-and-twenty-pound blow, may be counted upon to do the work without fail.
The cap itself is exploded by a spark running through a length of fuse, the length depending altogether upon the time required to reach a point of safety after the fuse is lighted.

The cap is really more dangerous to handle than is the dynamite itself.