Dr Helen Dick Megaw (1907-2002) was Assistant Director of
Research at the Cavendish Laboratory in Cambridge. In this
photograph she is shown setting a photogoniometer: a piece of
equipment used to take X-ray photographs of crystals. Behind her is
a ball-and-spoke model of the structure of afwillite, one of the
minerals she researched. One of Megaw's drawings of afwillite can
be seen in the next image.