Shedding Light on Dark Lanterns

I've always been intrigued by all the dark lanterns that appear in the Canon. Maybe that's because the term sounds contradictory -- aren't lanterns supposed to shed light?

The contradiction is easily resolved. Jack Tracy's classic and invaluable The Encyclopaedia Sherlockiana explains the device as "a lantern so constructed as to permit the light to be shut off without extinguishing the flame, and possessing a lens which allows the focusing of the beam. A single movable shutter acts as the reflector when moved behind the flame, and as a shade which shuts off the light when moved between the lens and the flame."

A pocket lantern and a bull's eye lantern are much the same. And I HAVE ONE! Shown above is one of my Father's Day presents from the wonderful Ann Brauer Andriacco, with whom I co-authored the three children who qualified me for a gift on that particular holiday.

Tracy cites references to dark lanterns in "The Adventure of the Speckled Band," "The Adventure of the Red-Headed League," "The Adventure of the Bruce Partington Plans," "The Adventure of Charles August Milverton," and "The Adventure of the Six Napoleons" -- during the commission of skullduggery, more often than not.

Holmes borrows a police sergeant's bull's eye lantern and also uses a pocket lantern in The Sign of Four. He employs a pocket lantern again to examine footprints in "The Adventure of Wisteria Lodge." Whatever it's called, it's cool to have one.