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
A. L. A. Himmelwright coal fired furnace with radiators in each room for heat; a similarly stone built garage of sufficient size to accommodate two large touring cars; and awnings and shutters with a concrete sidewalk all around. The walls are of granite, the floors and ceilings of poured concrete with steel reinforcement, the roof is lined with copper. Woodwork, plaster, brickwork, and concrete were all specced to be of "first class materials and workmanship". Himmelwright estimated its lifespan at 400–500 years. In 1913 Himmelwright published detailed engineering plans, drawings, and instructions on how to build replicas of the Stone House in a book,