sensation-waves, which spread from a focus, may be brought again to a focus by condensing them with an ear (Fig. 12). Here, across a little echo-cave, is hung a curtain, Ty. M., which is blown in and out as each air-wave beats against it; and, though the air-waves vary from 40 feet to 4 inches apart, they jump the distance quickly, and this curtain, taking an exact copy of each, in vibrations less than the thousandth part of an inch, sends them, through the tapping bones, Mall., Stp., to an inside curtain, F.o., where they are condensed again, and thrown through a liquid which fills the hollow inside of it. Here three thousand tuned nerves take up, each, its own acchording waves, and bear them to the brain; and thus the wild waves of an emotion passed from one "consciousness" to another in less than a second, proving that the "quickness of thought" is no metaphor. Through pipes, the sound of the voice may be heard nearly four miles, and conversation carried on at nearly a mile. Through the wire of the telephone, which has become literally the "thread of a conversation," sound, with all its qualities, is conveyed hundreds of miles, as we have already shown in a former article.
| THE SCIENTIFIC STUDY OF HUMAN TESTIMONY. |
By GEORGE M. BEARD, M. D.
I.
"Of what account are the most venerated opinions, if they be untrue? At best they are only venerable delusions."—Sir William Hamilton.
ABOUT two years ago I chanced to call on an educated professional man, who was much interested in the subject of delusions. He said, "I have been long wishing to see you, in order to get an explanation of some strange things that have happened under my observation." I inquired what these strange things were. He replied, as usual in such cases, by giving a detailed account of certain performances of a well-known trickster, to which I listened as politely as I could, and he concluded with this conundrum: "Now, how do you explain that?" I replied: "I do not know what happened, for there was no expert there to report. If I knew what happened, I could very likely explain it, for a knowledge of what happened would itself be the explanation." "But I have just told you what happened," he interposed, somewhat excitedly. "My wife and I both were there, and we saw it all, with our own eyes. Can't we trust our senses?" "Trust our senses?" I replied; "not at all. In science we never trust our senses." My friend was as much astonished and indignant as though he had been personally insulted, and I felt it to be prudent to withdraw from the house.
