Coal the heat and pressure of deep burial causes the loss of water, methane and carbon dioxide and an increase in the proportion of carbon. Thus first lignite (also called "brown coal"), then sub-bituminous coal, bituminous coal, and lastly anthracite (also called "hard coal" or "black coal") may be formed. The wide, shallow seas of the Carboniferous Period provided ideal conditions for coal formation, although coal is known from most geological periods. The exception is the coal gap in the Permian–Triassic extinction event, where coal is rare. Coal is known from Precambrian strata, which predate land plants—this coal is presumed to
Portrait of a Man with a Blue Chaperon bride's family most likely had not met the man and are dependent solely on the portrait for an indication of his means and character. Carol Richardson observes that the unidealised representation would have been a significant novelty and shock at the time, and that, complete with the evident skill of the painter, the verisimilitude would have given the sitter weight and creditability. The panel contains two illusionistic passages; the ring and his right hand appear to project out of the painting, while the minutely described fingers of his right hand seem to lie on a parapet positioned on what would