of the size gives a spark ten times as strong as Franklin's; or the electrometers and galvanometers of Faraday with the mirror-galvanometers and electrometers of Sir William Thomson. Yet, at the same time, let such an observer think of the possibilities of the next fifty years, for the advance of science is not in a simple proportion to the time, and the next fifty years will probably see a far greater advance than the one hundred years since the date of Franklin's electrical work has seen. Is not the state of our imagination like that of the shepherd-boy who lies upon his back, looking up at the stars of heaven, and trying to imagine what is beyond the stars? The only conclusion is that there is something far more than we have ever beheld. Is not the physicist of the future to have instruments delicate enough to measure the heat equivalent of the red and the yellow, the blue and the violet rays of energy?—instruments delicate enough to discover beats of light as we now discover those of sound—an apparatus which will measure the difference of electrical potential produced by the breaking up of composite grouping of molecules? The photographer of to-day speaks, in common language, of handicapping molecules by mixing gums with his bromide of silver, in order that their rate of vibration may be affected by the long waves of energy. Shall we not have the means of obtaining the mechanical equivalent of such handicapped vibrations? Or, turning to practical science, let us reflect upon the modern transmitter and the telephone, and contrast these instruments with the rude, so-called lover's telephone, which consists of two disks connected by a string or wire. What an almost immeasurable advance we see here! Would it not have been as difficult for Franklin to conceive of the electrical transmission of speech as for the shepherd-boy to conceive of other stars as far beyond the visible stars as the visible stars are from the earth?
Yes, we have advanced; but you will perceive that I have not answered the question, which filled the mind of Franklin, and which fills men's minds to day, "What is electricity?" If I have succeeded in being suggestive, and in starting trains of thought in your minds which may enlighten us all upon this great question, I have indeed been fortunate.
|CHILIAN VOLCANOES, ACTIVE AND EXTINCT.|
THE products of the extinct and the still active volcanoes of Chili, of which Pissis enumerates not less than seventy, are of contemporary origin with the diluvial and alluvial strata of the country. Of the gaseous emissions of their craters, it need only be mentioned that, as in all American volcanoes, chlorine is weakly represented. The