What is the origin of 'sleep tight'?
Read moreOne of the mysteries of the English language finally explained.
The bounding line of a series of Mohr circles drawn at different containing pressures for the stress on a body at the level at which it slips or fractures, the point at which a circle touches the line giving the plane along which slippage or fracturing occurs at a particular containing pressure.
1950s; earliest use found in Bulletin of the Geological Society of America.