Subgraywacke

Dark-coloured sedimentary rock that contains from 65 to 95 percent free quartz, in grains 0.06 to 2 mm in diameter, held together by a matrix with a low mud content and often a high carbonate content. Some geologists favour a definition of graywacke (q.v.) that permits no more than 75 percent free quartz in the rock, and they thus would class as subgraywackes those rocks with (1) over 25 percent

Absorption

In wave motion, the transfer of the energy of a wave to matter as the wave passes through it. The energy of an acoustic, electromagnetic, or other wave is proportional to the square of its amplitude—i.e., the maximum displacement or movement of a point on the wave; and, as the wave passes through a substance, its amplitude steadily decreases. If there is only a small fractional

Bridgend

Welsh  Pen-y-bont Ar Ogwr  town, Bridgend county borough, historic county of Glamorgan (Morgannwg), Wales, on the River Ogmore. It has grown up on the site of medieval riverside twin villages (Oldcastle and Newcastle) with a 12th-century castle and 15th-century hospice; a stone bridge was built over the river about 1435. Historically, Bridgend has been the market town for the western Glamorgan lowland and