The purifier is to be filled with milk of lime, made by mixing 1 part of Blacked lime with 25 parts of water. A very great Improvement in the purification of gas has been effected by Mr. Staffer, of England, by the employment of hydrated clay along with the lime employed for this purpose. Hydrated clay unites with the ammonia of the gas as with a base, and, at the same time, with its sulphuret of carbon as an acid, and thus removes both of these noxious impurities from the gas exposed to its influence. It assists also, in conjunction with the lime, in removing tarry vapor and other Impurities from the gas. The illuminating power of the gas is positively increased by the clay purification from 22 to 33 1/8 per cent.