Map, 'Penygraig Colliery explosion' by W [William] Galloway A map of Penygraig Colliery [Wales] with a colour-coded key showing the direction of the explosion, the direction in which 'coked coal dust was thrown against timbers etc', 'falls of roof caused by the explosion', 'falls of roof existing before the explosion', 'space from which coal has been removed and been replaced with stowing', 'galleries etc through which the flame of the explosion passed' and 'points at which there were indications of a high temperature'. Subject: Chemistry / Physics A print of this map was published in volume 33 of the Proceedings of the Royal Society alongside the paper 'On the influence of coal-dust in colliery explosions. No. III'. 1882