Letter from Thomas Gold to Dr Murray Gell-Mann, Department of Physics, CAllifornia Institute of Technology, Pasadena, California 91109 Concerning the question of pair creation or something of that kind settin a limit to the strength of magnetic fields. Notes there is a paper in 1968 concerned with that subject, and in view of his remarks he supposes it is wrong, but as it is a matter of great importance to astronomy did not want to ignore it without bringing it to Gell-Mann's attention 16 December 1971