EXPERIMENTS OF CISTERNAY DUFAY

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 Francois 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 313h721d man who had ever

contributed to the annals of the academy investigations in every

one of the six subjects admitted by that institution as worthy of

recognition. Dufay upheld his reputation in this new field of

science, making many discoveries and correcting many mistakes of

former observers. In this work also he proved himself a great

diplomat by remaining on terms of intimate friendship with Dr.

Gray--a thing that few people were able to do.

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 vitae, 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 stand and that set on a plate of glass, or

on the brim of a drinking-glass, previously chafed, or otherwise

warmed), I have found, upon trial, that the same thing happened

to all bodies without exception, whether solid or fluid, and that

for that purpose 'twas sufficient to set them on a glass stand

slightly warmed, or only dried, and then by bringing the tube

near them they immediately became electrical. I made this

experiment with ice, with a lighted wood-coal, and with

everything that came into my mind; and I constantly remarked that

such bodies of themselves as were least electrical had the

greatest degree of electricity communicated to them at the

approval of the glass tube."

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 contribute much to electricity, but three

experiments convinced me to the contrary. The first, that by

warming the pieces of gauze neither the black nor white pieces

obstructed the action of the electrical tube more than those of

the other colors. In like manner, the ribbons being warmed, the

black and white are not more strongly attracted than the rest.

The second is, the gauzes and ribbons being wetted, the ribbons

are all attracted equally, and all the pieces of gauze equally

intercept the action of electric bodies. The third is, that the

colors of a prism being thrown on a white gauze, there appear no

differences of attraction. Whence it proceeds that this

difference proceeds, not from the color, as a color, but from the

substances that are employed in the dyeing. For when I colored

ribbons by rubbing them with charcoal, carmine, and such other

substances, the differences no longer proved the same."

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" ("isolee"), as he

said, first making use of this term.