The note by J. W. Crosbie prompts the writer to the following comments. Lecky's Tables2 do not cover vertical angles below the geometrical horizon (zenith distance =90°), or, indeed, angles of less than 10’ above it. Crosbie's method, also, does not cater for angles below the geometrical horizon, though it could be adapted to do so. His extraordinary evolutions with the traverse tables, undertaken to avoid solving a quadratic equation by orthodox methods, are fascinating. Surely, a slide rule, with which the equation could be solved in a few seconds, is available in today's chartroom.