Luminous phosphorus applied to the hound

Luminous phosphorus applied to the hound was the material device that made a living dog appear to be the family’s supernatural monster. It gave a physical, recoverable explanation for the creature’s apparent glow, while helping Roger Baskerville exploit the legend as a weapon of fear.

Appearance and Properties

After the hound was killed, Dr. Watson found that its muzzle still appeared to glow. When he touched it, the substance transferred to his fingers, revealing that the light came from a coating rather than from the animal itself. He identified the material as phosphorus.

Sherlock Holmes explained that the preparation had been devised so that it would not produce a smell capable of interfering with the hound’s scenting ability. The detail matters to the deception’s practical design: the substance had to make the dog look uncanny without disabling its ability to track its intended victim.

Use in the Scheme

Holmes connected the luminous mixture to the family legend and to the effort to frighten Sir Charles Baskerville to death. The coating made the dog’s appearance seem to confirm the old tale, turning a trained animal into an apparent supernatural threat. Fear could itself serve the scheme: a person confronted by such a creature might flee, while witnesses on the moor might hesitate to investigate closely.

The dog could be concealed, but its cries could not always be suppressed. Holmes noted that it could be kept in the out-house at Merripit House in an emergency, though doing so carried a risk; the luminous preparation was part of a larger plan that depended on managing both the animal and the impression it made.

Discovery and Significance

The coating’s physical residue helped resolve the mystery after the hound’s death. At the hidden site on the island in Grimpen Mire, the investigators found a tin containing paste that Holmes identified as the luminous mixture used on the animal. The discovery linked the apparent supernatural light to a material substance and the creature to Roger Baskerville’s concealed operation.

The phosphorus did not create the hound or its capacity to pursue. Its function was to transform how the animal was seen: it gave an ordinary explanation for the ghostly appearance while preserving the terror on which the scheme relied. In that way, the substance joined practical concealment to the family legend, and helped Holmes expose the mechanism behind the supposed curse.