Chap. VIII Experiments Which May Be Performed Without the Assistance of the Battery
To shew the Galvanic light.
Place a piece of zinc upon your tongue, and a piece of silver between your cheek and upper jaw; then move your tongue so as to bring the two metals in contact with each other, and you will perceive a very curious sensation upon your tongue, accompanied by a cool sub-acid taste,21 and at the same time you will see a flash of light, whether your eyes be open or closed. The sub-acid taste resembles, in a degree, that produced by electricity.22