or less increase and diminution of pressure, that is, by differential actions. We shall presently see that this is not the case with the microphone. In the first place, the carbon contact is effected in the latter instrument on other carbons and not with platinum disks, and these contacts are multiple. In the second place, the pressure exerted on all the points of contact is excessively slight, so that the resistances can be varied in an infinitely greater ratio than in Mr. Edison’s system; and for this very reason it is possible to magnify the sounds. In the third place, a microphone can be made of other substances besides carbon. Finally, no vibrating disk is needed to make the microphone act; the simple medium of air is enough, so that it is possible to work the instrument from some little distance. We do not therefore see the grounds for Mr. Edison’s assertions, and especially for the way in which he has spoken of Messrs. Hughes and Preece, who are well known in science and are in all respects honourable men. I repeat my regret that Mr. Edison should have made this ill-judged attack on them, since it must injure himself, and is unworthy of an inventor of such distinction. If we look at the question from another point of view, we must ask Mr. Edison why, if he invented the microphone, he did not make us acquainted with its properties and results. These results are indeed startling, since the microphone has in so short a time attracted general attention; and it is evident that the clear-sighted genius of this celebrated American inventor would have made the most of the discovery if it were really his. The only justification for Mr. Edison’s claim consists in his ignorance of the purely scientific discoveries made in Europe, so that he supposed the invention of the microphone to be wholly involved in the principle which he regards as his peculiar discovery.