Fourth letter from Harold Spencer Jones, to John David Griffith Davies, regarding a paper 'The Earth's magnetic field in Southern Africa at the epoch, 1 July 1930' by E N Grindley Sectional Committee: Not stated [Physics] Sees no difficulty in numbering the smaller charts. The larger charts should be reproduced on a larger scale, in order for all the details to be included. Could these be printed as folders on a 16" by 12" size? [Published in the Philosophical Transactions of the Royal Society] No received date. 18 July 1945