Each of the lateral walls (16) has a crack initiator means (26).

The presence of these particles exhances the priming of erosive discharges.

A striker circuit (31) is provided for starting the lamp (10).

All campfires must be built inside of a campfire ring.

Each crack ends, at each end, at a crack arresting feature.

At least one energy absorbing crack penetrates the body.

An approximate position of the second fracture is determined from a percentage of the average of the first fracture dimension and the second fracture dimension.

The energy absorbing crack has opposed crack faces with the faces touching along substantially the entire length of the crack.

If the borehole contains a fissure (71) the Kevlar provides a rigid bridge over the fissure, and prevents the packing-seal from ballooning out into the fissure.

The well may then be fractured at the approximate position of the second fracture and may be fractured at the approximate position of the third fracture.

Matrix and fracture flow equations for fluid flow in the matrix and fracture blocks are obtained.

Consequently, vertical crack can grow easily and growth of horizontal crack can be suppressed.

Very serious risk of loosening or cracking.

through-cracking of any friction ring

Very serious risk of loosening or cracking.