ABSTRACT
This chapter is based on the opening survey given by the writer as Vice-President of Section A (Physics) of the British Association for the Advancement of Science at its Norwich Meeting on 11 September 1984; it is now suitably updated. A shortened version of the address was published in Dr G. T. Meaden's Journal of Meteorology, vol. 9, no. 92,1984, pp. 237–42.
