A remarkably delicate balance between the small scale phenomena of atomic and nuclear physics and the large scale phenomena of astronomy and cosmology is required for the Universe to be hospitable to chemically based life. Efforts to prove that this must be so are sometimes dignified by the name anthropic principle.

Some flakes detached in a controlled manner have characteristics of conchoidal fracture.

There's merit to the saying, Dress for the slide, not the ride. Even at a modest 30 miles per hour this is.

In addition to its work on longwall faces, the A.B. Fifteen has been adapted for shortwall work either as undercutter or as overcutter, particular care having been taken to give it increased manoauvrability by the provision of special pulleys, and increased mobility by the addition of a tilting underframe.