The popular exhibitions of the speaking-telephoneduring the past six months, together withnumerous newspaper articles, have created a widespreadinterest in the instrument; and it has beenthought that a small book explanatory of itsaction would meet a public want.
It has seemed to be necessary to call attentionto the various phenomena and inter-actions ofthe forces involved; and hence the author hasattempted to make plain and intelligible thephenomena of electricity, magnetism, and sound.Cuts have been inserted where they could be usefulin making the mechanical conditions more intelligible;and a table of tone-composition has been[vi]devised, which shows at a glance the constituentsof the sounds of various musical instruments.
As the speaking-telephone, in which magneto-electriccurrents were utilized for the transmissionof speech and other kinds of sounds, was inventedby me, I have described at some length my firstinstrument, and have also given explicit directionsfor making a speaking-telephone which I know, bytrial, to be as efficient as any hitherto made; butnothing in the book is to be taken as a dedicationof the invention to the public, as steps have alreadybeen taken to secure letters-patent according to thelaws of the United States.
College Hill, Mass.
Some of the phenomena of electricity are manifestedupon so large a scale as to be thrust uponthe attention of everybody. Thus lightning, whichaccompanies so many showers in warm weatherin almost every latitude, has always excited insome individuals a superstitious awe, as being anexhibition of supernatural agency; and probablyevery one feels more or less dread of it during athunder-shower, and this for the reason that itaffects so many of th