"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.