tone down the stone to a sober tint. Unhappily of late years there has been much firing of the furze and heather on the moor, and the flames destroy the beautiful lichens and mosses, and leave the old stones white and ghostly, not to be reclothed with the old tints for centuries.
I do not think that we have any idea of the slowness with which the lichens spread; a century to them is nothing—it passes as a watch in the night. There is a granite post I often go by. It was set up just seventy years ago, and on it the largest golden circle of the Physcia parietina has attained the diameter of an inch. Mr. Parfitt mentions in connection with it a rocky crag at Baggy Point, North Devon, where it covers the whole surface with a coat of golden colour. It spreads more rapidly on slate than it does on granite, and especially on such slates as are liable to rapid disintegration. The Woodland and the Coryton slates are readily attacked by it. The growth begins with a splash about the size of a sixpence, and increases to that of a plate, when the centre breaks up, and the ring becomes detached in fragments which meet others, and so appear to cover the rock or roof.
One of the most beautiful of the lichens on the moor is the coral moss, Sphœrophoron coralloides. It is a pale greenish- white, upright-growing lichen, that forms a cup, and somewhat resembles an old Venetian wineglass. Then points of brilliant scarlet form round the lip of the cup, and increase in size till the whole presents a wonderful appearance as of sealing-wax splashed over the soil. It is not con-