Letter from [Alan Archibald Campbell] Swinton, to C. P. MacCarthy [Esquire] Responding to a previous letter, opining that it would be interesting to try the Marconi amplifier in comparison with the one obtained from Sullivans and that by connecting first the one and then the otherm obe could see whihc gave the best results. Offers to partake if he can be of any use but that it is chiefly a matter for experts in reading by the Optophone, to see which amplifier gives the clearest signals. Mentions that in the next day's "Nature" his account of what they already did in the matter is due to appear. 2 March 1921