Copy letter from Robert William Frederick Harrison to Professor J [John] S [Sealy Edward] Townsend FRS 'With regard to your letter asking for an erratum slip of correction for your paper published in Proceedings [of the Royal Society], March 14, I have been authorised to print the corrections at the foot of the contents of the volume when it is completed. Sir Joseph Larmor thinks the mistakes are sufficiently obvious to enable anyone to verify the readings for himself.' 3 May 1911