Copy letter from Robert William Frederick Harrison, to Dr E W Marchant, The University, Liverpool The paper referred to in their letter of 30 june was published in the May number of 'Proceedings [of the Royal Society]' Series A. The only thing possible for the Royal Society to do would be to add the reference to a list of errata at the end of the present volume, which will be closed about the end of the month. 2 July 1913