Prophylactics against magic
Surprisingly, we learn that one of Mr Norrell's own spells was rendered harmless by a bible, and by the quick thinking of a dissipated man about town called Scrope Davies. It came about in the following manner. At one time Mr Norrell very much wished to suppress any knowledge of Strange's actions in Venice, and fearful lest some letters sent to Davies from there by his intimate friend Lord Byron would throw light upon matters Mr Norrell preferred should be kept in the dark, he cast a spell on them. This would in a very short time have erased any writing they contained. As it happened however, Davies was present as the spell began to work, and realising what was happening he swiftly caught up the letters and thrust them between the pages of a bible - and there it seems they were safe from Mr Norrell's interference, the bible entirely preventing the spell from doing its work.
Jonathan Strange also candidly admits, in the course of a conversation with the gentleman with the thistle-down hair, that many things interfere with his abilitiy to perform magic. "A salt-cellar, a rowan-tree, a fragment of the consecrated host - these all make me feel decidedly unsettled. I do not say I cannot do magic in their presence, but I always need to take them into account..."  Salt, rowan-trees and communion bread are of course all traditionally considered protection against witchcraft; but from what Mr Strange says, they interfere even with the practice of legitimate magic. Certainly salt (along with iron and the colour red) is one of the substances which an ancient spell recommends as able to undo the power of certain enchantments. The same spell suggests the light of the moon is often beneficial - and indeed perhaps any light is good.
There is a curious reference in the King's Prophecy to his blood being conserved by his enemies in vessels of 'silver and ivory'. Since the enemies in question are thralls of Lucifer they cannot be supposed to be performing this act for any good reason (such as respect or veneration). Rather one doubts they wish to possess some intimate effect of the King in order to work magic upon it and do him harm; and they also wish to keep it in a place where he will be unable to retrieve it. To conserve such an item therefore in a vessel of silver may indicate yet another prophylactic, for silver has often been credited as a protection against magic; and thus silver knives, bullets etc have often been described as a certain means of vitiating magical power. In his portrait at Windsor however the king is shown holding an ivory wand and therefore ivory itself cannot be classed among prophylactics, though the Ancient Egyptians seem to have held that it could be used to control the power of demons.
Another kind of paraphernalium was used to ward off (black) magic: the witch ball, a hollow sphere of plain or stained glass hung in cottage windows in 18th century England to ward off evil spirits, witch's spells or ill fortune.
The witch ball originated among cultures where witches were considered a blessing and these witches would usually "enchant" the balls to enhance their potency against evils. Witch balls entice evil spirits with their bright colours; the strands inside the ball would then capture the spirit and prevent it from escaping.
Witch balls sometimes measure as large as seven inches (18cm) in diameter.
|The word witch ball may be a corruption of watch ball because it was used to ward off, guard against, evil spirits.|
Because they look similar to the glass balls used on fishing nets, witch balls are often associated with sea superstitions and legends. In the Ozark Mountains, a witch ball is made from black hair that is rolled with beeswax into a hard round pellet about the size of a marble and is used in curses. In Ozark folklore, a witch that wants to kill someone will take this hair ball and throw it at the intended victim; it is said that when someone in the Ozarks is killed by a witch's curse, this witch ball is found near the body.