Letter from Thomas Lydwell Eckersley, on his paper with F T Farmer 'Short period fluctuations in the characteristics of wireless echoes from the ionosphere' to the Secretary of the Royal Society He has read through the paper thoroughly and he can't find anything that may be of value to the enemy. The technique described is 'a little too elaborate' to be made use of and the results won't have any immediate bearing. He has enclosed two copies of the summary and eight prints of the photographs, which are of better quality. [Published in Proceedings of the Royal Society A, 1945]. Endorsed on recto as received 16 September 1940. 3 September 1940