"Le Bon has also observed that quinine sulphate, if heated and then allowed to cool, possesses for a short time the property of discharging both positively and negatively electrified bodies. It is necessary, however, to draw a sharp line of distinction between phenomena of this kind and those exhibited by the naturally radio-active bodies. While both, under special conditions, possess the property of ionizing the gas, the laws controlling the phenomena are quite distinct in the two cases. ...the activity of the naturally radio active bodies is spontaneous and permanent. It is exhibited by all compounds and is not as far as is yet known altered by change in the chemical or physical conditions."