INVISIBLE INK

I bought a bottle of this high-quality (cobalt chloride) invisible ink from J. Herbin, a "maker of fine specialty inks." For the maiden voyage, I tried my best at Edgar Allen Poe's "Gold Bug" - in the story, an illustration of a species of scarab has an invisible ink skull drawn beneath it, the ink activated by heat.

SECRET HOBO SIGNS

The Internet has needed a good directory of old railyard hobo signs - the signs that hoboes used to chalk onto walls and trains to communicate with each other. Behold the Super Secret Clubhouse index of "Secret Hobo Signs". . .
[click to enlarge]

HOBO SIGNS

World Famous Design Junkies has a nice collection of "Hobo Signs" excerpted from the 1969 book "Signs, Symbols, and Signets" by Ernst Lehner.