|The paper Walker requires was ready many years ago . This makes it rather difficult for the Society to comply with Walker's request for a copy. The Society's practice is to leave to authors the choice of journals to which they would like their papers to be sent. Suggest the best thing would be for Walker to write to Messrs C G Lamb and W G Wilson care of Professor Ewing FRS, Engineering Laboratory, Cambridge, The paper appeared in 'Proceedings [of the Royal Society]' number 419 and is priced at two shillings. Should Walker reproduce the paper he should of course carefully acknowledge the source.