A few years ago every student of chemistry was more or less agitated by the thought that more than half of every clay bank was composed of metal nearly as valuable, or at least as costly, as gold. This is aluminum. By all the methods then known it was a very difficult and expensive process to extract the metal from the clay. At length, by the perfecting of the dynamo, the chemist had under his control great and powerful electric currents which enabled him to unlock any chemical compound however refractory and isolate its elements. As a result aluminum became common enough and cheap enough for even kitchen utensils. The metal calcium which a short time ago was an exceedingly rare substance worth $40 an ounce is now fairly abundant and cheap for chemical experiments, although it has no qualities which will give it an extended use. Powerful electric currents, such as are obtained at Niagara, enable us to combine elements into hitherto unknown chemical compounds. Carbon and silicon are made to unite to form carborundum, which vies with the diamond for hardness. Carbon and calcium unite to form calcium carbide, used with water to form acetylene gas. In such processes the intense heat of the electric arc--perhaps 6000 degrees--is employed, together with the electrolytic action of the current, to separate and combine substances. Enormous currents are used in the electric furnaces for producing chemical reactions--from 1000 to 30,000 amperes at a time. Electric currents passing through the human body expend their energy partly in heat and partly in electrolysis. So simple and harmless a thing as common salt would become a virulent poison if it could be electrolized in the body into its elements _sodium_ and _chlorine_.