XIV
PROGRESS IN ELECTRICITY FROM GILBERT
AND VON GUERICKE TO FRANKLIN
A History of Science: in Five Volumes. Volume II: The Beginnings of Modern Science | ||
EXPERIMENTS OF CISTERNAY DUFAY
So far England had produced the two foremost workers in electricity. It was now France's turn to take a hand, and, through the efforts of Charles François de Cisternay Dufay, to advance the science of electricity very materially. Dufay was a highly educated savant, who had been soldier and diplomat betimes, but whose versatility and ability as a scientist is shown by the fact that he was the only man who had ever contributed to the annals of the academy
Almost his first step was to overthrow the belief that certain bodies are "electrics'' and others "non-electrics''—that is, that some substances when rubbed show certain peculiarities in attracting pieces of paper and foil which others do not. Dufay proved that all bodies possess this quality in a certain degree.
"I have found that all bodies (metallic, soft, or fluid ones excepted),'' he says, "may be made electric by first heating them more or less and then rubbing them on any sort of cloth. So that all kinds of stones, as well precious as common, all kinds of wood, and, in general, everything that I have made trial of, became electric by beating and rubbing, except such bodies as grow soft by beat, as the gums, which dissolve in water, glue, and such like substances. 'Tis also to be remarked that the hardest stones or marbles require more chafing or heating than others, and that the same rule obtains with regard to the woods; so that box, lignum vitæ, and such others must be chafed almost to the degree of browning, whereas fir, lime-tree, and cork require but a moderate heat.
"Having read in one of Mr. Gray's letters that water may be made electrical by holding the excited glass tube near it (a dish of water being fixed to a
His next important discovery was that colors had nothing to do with the conduction of electricity. "Mr. Gray says, towards the end of one of his letters,'' he writes, "that bodies attract more or less according to their colors. This led me to make several very singular experiments. I took nine silk ribbons of equal size, one white, one black, and the other seven of the seven primitive colors, and having hung them all in order in the same line, and then bringing the tube near them, the black one was first attracted, the white one next, and others in order successively to the red one, which was attracted least, and the last of them all. I afterwards cut out nine square pieces of gauze of the same colors with the ribbons, and having put them one after another on a hoop of wood, with leaf-gold under them, the leaf-gold was attracted through all the colored pieces of gauze, but not through the white or black. This inclined me first to think that colors
In connection with his experiments with his thread suspended on glass poles, Dufay noted that a certain amount of the current is lost, being given off to the surrounding air. He recommended, therefore, that the cords experimented with be wrapped with some non-conductor—that it should be "insulated'' ("isolée''), as he said, first making use of this term.
XIV
PROGRESS IN ELECTRICITY FROM GILBERT
AND VON GUERICKE TO FRANKLIN
A History of Science: in Five Volumes. Volume II: The Beginnings of Modern Science | ||