IN connection with the subject of mechanical telephones, which has been occupying public attention lately, there is a note by Mr. Miller in a recent number of NATURE, regarding certain experiments made in 1878 on the propagation of sound. With reference to this, Prof. Wernhold, of Chemnitz, writes to me, saying that as early as 1870 he had shown that human speech could be transmitted very distinctly through stretched wires or threads, and mentions that the results of his researches were published in an article on “The Transmission of Human Speech through an Iron Wire,” in Carl's “Repertorium fur Experimental Physik,” Band vi., Serie 168. As your correspondent will probably like to refer to this, may I ask you to kindly publish this letter?