Demonology and Devil-lore

Three Friars, says a legend, hid themselves near the Witch Sabbath orgies that they might count the devils; but the Chief of these, discovering the friars, said—‘Reverend Brothers, our army is such that if all the Alps, their rocks and glaciers, were equally divided among us, none would have a pound’s weight.’ This was in one Alpine valley. Any one who has caught but a glimpse of the world’s Walpurgis Night, as revealed in Mythology and Folklore, must agree that this courteous devil did not overstate the case. Any attempt to catalogue the evil spectres which have haunted mankind were like trying to count the shadows cast upon the earth by the rising sun. This conviction has grown upon the author of this work at every step in his studies of the subject. 
In 1859 I contributed, as one of the American ‘Tracts for the Times,’ a pamphlet entitled ‘The Natural History of the Devil.’ Probably the chief value of that essay was to myself, and this in that its preparation had revealed to me how pregnant with interest and importance was the subject selected. Subsequent researches in the same direction, after I had come to reside in Europe, revealed how slight had been my conception of the vastness of the domain upon which that early venture was made. In 1872, while preparing a series of lectures for the Royal Institution on Demonology, it appeared to me that the best I could do was to print those lectures with some notes and additions; but after they were delivered there still remained with me unused the greater part of materials collected in many countries, and the phantasmal creatures which I had evoked would not permit me to rest from my labours until I had dealt with them more thoroughly.