Carbon exists in a variety of forms— charcoal, anthracite lamp-black, diamond, are all different forms or states of the same ele ment. There is but a small amount of car bon in the mineral world—none, indeed, but what is supposed to have been.of organic ori gin. But in the organized world it is a funda mental and universal element. When wood or coal burns or decays, or when living things perish, their , carbon combines with oxygen, and the substance formed is known as carbo nic acid. This is a universal product of com bustion, whether in the ungovernable confla gration or the measured respiration of the living animal. Carbonic acid is a heavy gas —it extinguishes fire and destroys all animal life. If an animal attempts to breathe it pure, there is spasmodic closure of the glottis and the animal dies as speedily as if strangled with a cord. It breathed,when diluted with 90 per cent, of air, it acts as a narcotic poison, inducing, sleep, torpor, and death. Carbonic acid gas and steam are employed in the Fire Annihilator to extinguish flame. There is a small portion of carbonic acid gas in the at-mosphere,nameJy, one gallon diffused through 2,000 gallons of air. This may be increased ten-told or to one half per cent—more than this is injurious. A man exhales about 20 cubic feet of carbonic acid per day, which would therefore vitiate or spoil 4,000 cubic feet of air each day, or equal to all that is to be found over a space of 56 square feet to the top of the atmosphere annually. Larger quantities still are generated by combustion and decay. Water has a strong attraction for carbonic acid and absorbs much ol it. It then acquires new properties, particularly thepow-erof dissolving a great number of minerals.