Where properties are much divided, it is always necessary to maintain a thick barrier of unwrought coal between the boundary of the mine and the neighbouring workings, especially if the latter are to the dip. If a prominent line of fault crosses the area it may usually be a convenient division of the fields into sections or districts.
In France and Germany the method of filling the space left by the removal of the coal with waste rock, quarried underground or sent down from the surface, which was originally used in connexion with the working of thick inclined seams by the method of horizontal slices, is now largely extended to long-wall workings on thin seams, and in Westphalia is made compulsory where workings extend below surface buildings, and safety pillars of unwrought coal are found to be insufficient.
The bishop and clergy choose a suitable spot, and erect twelve large stones unwrought and unpolished around the central rock of the altar, and on these the walls of the church are laid.
Of the total exports that of timber, wrought and unwrought, represents 50%; the other principal exports with approximate percentage are: iron and steel 13.5, iron ore 3.6, machinery and implements 3.2, and other iron and steel goods 2.7; butter Io; paper 3.4; carpentry work 3; matches 2.3.
Lord Avebury regards it as a temple of the Bronze Age (150o - 1000 B.C.), though apparently it was not all erected at one time, the inner circle of small unwrought, blue stones being probably older than the rest (Prehistoric Times).