Cave painting is an accretive practice, layering pigment over rock, but the making of a petroglyph is subtractive; inch by inch, rock matter has been chinked away. What a petroglyph fundamentally consists of is: a gap. That the effect of a petroglyph is to recall the form of an animal—that it creates the apprehension of a presence—is a mental feat, for a petroglyph is an artwork made out of absence.
