But it must be confessed that man is dreadfully clumsy about it yet.  He takes a thousand horsepower engine and an electric furnace at several thousand degrees to get carbon into combination with hydrogen while the little green leaf in the sunshine does it quietly without getting hot about it.  Evidently man is working as wastefully as when he used a thousand slaves to drag a stone to the pyramid or burned down a house to roast a pig.  Not until his laboratory is as cool and calm and comfortable as the forest and the field can the chemist call himself completely successful.

But in spite of his clumsiness the chemist is actually making things that he wants and cannot get elsewhere.  The calcium carbide that he manufactures from inorganic material serves as the raw material for producing all sorts of organic compounds.  The electric furnace was first employed on a large scale by the Cowles Electric Smelting and Aluminum Company at Cleveland in 1885.  On the dump were found certain lumps of porous gray stone which, dropped into water, gave off a gas that exploded at touch of a match with a splendid bang and flare.  This gas was acetylene, and we can represent the reaction thus: 

  CaC_{2} + 2 H_{2}O —­> C_{2}H_{2} + CaO_{2}H_{2}

  calcium carbide added to water _
    gives_ acetylene and slaked lime

We are all familiar with this reaction now, for it is acetylene that gives the dazzling light of the automobiles and of the automatic signal buoys of the seacoast.  When burned with pure oxygen instead of air it gives the hottest of chemical flames, hotter even than the oxy-hydrogen blowpipe.  For although a given weight of hydrogen will give off more heat when it burns than carbon will, yet acetylene will give off more heat than either of its elements or both of them when they are separate.  This is because acetylene has stored up heat in its formation instead of giving it off as in most reactions, or to put it in chemical language, acetylene is an endothermic compound.  It has required energy to bring the H and the C together, therefore it does not require energy to separate them, but, on the contrary, energy is released when they are separated.  That is to say, acetylene is explosive not only when mixed with air as coal gas is but by itself.  Under a suitable impulse acetylene will break up into its original carbon and hydrogen with great violence.  It explodes with twice as much force without air as ordinary coal gas with air.  It forms an explosive compound with copper, so it has to be kept out of contact with brass tubes and stopcocks.  But compressed in steel cylinders and dissolved in acetone, it is safe and commonly used for welding and melting.  It is a marvelous though not an unusual sight on city streets to see a man with blue glasses on cutting down through a steel rail with an oxy-acetylene blowpipe as easily as a carpenter saws off a board.  With such a flame he can carve out a pattern in a steel plate in a way that reminds me of the days when I used to make brackets with a scroll saw out of cigar boxes.  The torch will travel through a steel plate an inch or two thick at a rate of six to ten inches a minute.