stratum

It is built of alternate strata of brick and clay, and the sides correspond to the direction of the meridians and parallels.

An illuminating article in a recent issue of the Eastern Region's Civil Engineering News points out that where coal is worked over a reasonably large area, it is not only the whole of the strata above the workings, but also an area beyond which is liable to subside at varying rates after the coal has been removed.

Computers that synchronize themselves to the stratum 1 time servers are known as stratum 2 time servers if they allow others to synchronize to them, and so on.