Letter from [William George] Armstrong, Cragside, Rothbury, to [Alan Archibald Campbell] Swinton, 66 Victoria [Street], London, S.W Asks whether Swinton can receive him at his lodgings on Thursday morning and afterwards take him to [Alfred] Apps, as the last coil was splending for long sparks. Informs that he put about 8 times as much current from his multiple machine than he can get from the 10 inch coil. His current question is what length [?] the secondary wire should be. 24 June 1892