of coal and oil.  But the coal and oil are irrecoverable while the wood may be regrown, though it would require another three hundred years and more to grow some of the trees we have cut down.  For fuel a pound of coal is about equal to two pounds of wood, and a pound of gasoline to three pounds of wood in heating value, so there would be a great loss in efficiency and economy if the world had to go back to a wood basis.  But when that time shall come, as, of course, it must come some time, the wood will doubtless not be burned in its natural state but will be converted into hydrogen and carbon monoxide in a gas producer or will be distilled in closed ovens giving charcoal and gas and saving the by-products, the tar and acid liquors.  As it is now the lumberman wastes two-thirds of every tree he cuts down.  The rest is left in the forest as stump and tops or thrown out at the mill as sawdust and slabs.  The slabs and other scraps may be used as fuel or worked up into small wood articles like laths and clothes-pins.  The sawdust is burned or left to rot.  But it is possible, although it may not be profitable, to save all this waste.

In a former chapter I showed the advantages of the introduction of by-product coke-ovens.  The same principle applies to wood as to coal.  If a cord of wood (128 cubic feet) is subjected to a process of destructive distillation it yields about 50 bushels of charcoal, 11,500 cubic feet of gas, 25 gallons of tar, 10 gallons of crude wood alcohol and 200 pounds of crude acetate of lime.  Resinous woods such as pine and fir distilled with steam give turpentine and rosin.  The acetate of lime gives acetic acid and acetone.  The wood (methyl) alcohol is almost as useful as grain (ethyl) alcohol in arts and industry and has the advantage of killing off those who drink it promptly instead of slowly.

The chemist is an economical soul.  He is never content until he has converted every kind of waste product into some kind of profitable by-product.  He now has his glittering eye fixed upon the mountains of sawdust that pile up about the lumber mills.  He also has a notion that he can beat lumber for some purposes.

VII

SYNTHETIC PLASTICS

In the last chapter I told how Alfred Nobel cut his finger and, daubing it over with collodion, was led to the discovery of high explosive, dynamite.  I remarked that the first part of this process—­the hurting and the healing of the finger—­might happen to anybody but not everybody would be led to discovery thereby.  That is true enough, but we must not think that the Swedish chemist was the only observant man in the world.  About this same time a young man in Albany, named John Wesley Hyatt, got a sore finger and resorted to the same remedy and was led to as great a discovery.  His father was a blacksmith and his education was confined to what he could get at the seminary of Eddytown, New York,