A road maybe used as a self-acting or gravitating incline when the gradient is r in 30 or steeper, in which case the train is lowered by a rope passing over a pulley or brake drum at the upper end, the return empty train being attached to the opposite end of the rope and hauled up by the descending load.
In a large colliery where the shafts are situated near the centre of the field, and the workings extend on all sides, both to the dip and rise, the drawing roads for the coal may be of three different kinds - (r) levels driven at right angles to the dip, suitable for horse roads, (2) rise ways, known as jinny roads, jig-brows, or up-brows, which, when of sufficient slope, may be used as self-acting planes, i.e.
The earliest form of the Grail story, the Gawain- Bleheris version, exhibits a marked affinity with the characteristic features of the Adonis or Tammuz worship; we have a castle on the sea-shore, a dead body on a bier, the identity of which is never revealed, mourned over with solemn rites; a wasted country, whose desolation is mysteriously connected with the dead man, and which is restored to fruitfulness when the quester asks the meaning of the marvels he beholds (the two features of the weeping women and the wasted land being retained in versions where they have no significance); finally the mysterious food-providing, self-acting talisman of a common feast - one and all of these features may be explained as survivals of the Adonis ritual.
Here the Grail, the chalice of the Last Supper, is at the same time, as in the Gawain stories, self-acting and food-supplying.
Gravity or self-acting planes are for lowering loaded cars, one or more at a time, from a higher to a lower level.
According to Leibnitz, while each immaterial element is a monadic substance and self-acting secondary cause, God is the primary cause of all.