The modalities of appearance mark Roni Horn's series of 36 head shots of a clown. Originally seen in her Clowd and Cloun installation, a series of alternating images on the two motifs of the cloud and the clown, Horn's stunning photographs of the inevitable clown (he always looks the same) disintegrate the very consistency that makes a clown recognizable as a clown. The clown is a constant, a symbolic form whose identity is rooted in a conventionally...