An apparatus has been invented by a French engineer of the name of Otto, which is of very simple construction and takes up very little space. It is intended to use in the purification of water by electricity. The machine consists principally of a small closed box, the metal cover of which is made conductory with the bottom. In the box are an ozone developer, an interrupter and a tin tube. Through the latter the ozone, which first has to pass through a cotton stopper to free it from dust and germs contained in the air. is conducted into the water and mixed therewith. If much ozone has been absorbed, the water becomes phosphorescent in the dark. The most important part of the apparatus is the “mixer,” the action of which can be interrupted at will. The apparatus is capable of purifying about sixty gallons of water an hour, and the cost per hour is about the same as that of an ordinary electric incandescent light.