Abstract
The disclination s= + 1/2 in a nematic liquid crystal is observed to have some twist character so that it resembles half of a disclination s = +1 with circumferential directors at infinity and an escaped core. It therefore has helicity. When the disclination is trapped near the surface, its core lies just outside the surface. The helicity and the position of the core above or below the surface can both be determined by polarized light, or by decoration of the surface with dust or water droplets, combined with observation of the change of these patterns when the surface is gently blown parallel to the line of the disclination. The surface disclination line is sharply kinked at nodes where the helicity reverses. The director pattern at the surface almost always shows an asymmetry which (from geometrical necessity) is independent of the helicity, but always reverses at a node. It is possible by blowing on the surface to reverse the asymmetry of each segment of the line, so that the rule of reversal of asymmetry at a node is still preserved. Rough qualitative explanations of the observations are given.