On a plain rush hurdle a silkworm lay
  When a proud young princess came that way. 
  The haughty daughter of a lordly king
  Threw a sidelong glance at the humble thing,
  Little thinking she walked in pride
  In the winding sheet where the silkworm died.

But so far we have not reached a stage where we can altogether dispense with the services of the silkworm.  The viscose threads made by the process look as well as silk, but they are not so strong, especially when wet.

Besides the viscose method there are several other methods of getting cellulose into solution so that artificial fibers may be made from it.  A strong solution of zinc chloride will serve and this process used to be employed for making the threads to be charred into carbon filaments for incandescent bulbs.  Cellulose is also soluble in an ammoniacal solution of copper hydroxide.  The liquid thus formed is squirted through a fine nozzle into a precipitating solution of caustic soda and glucose, which brings back the cellulose to its original form.

In the chapter on explosives I explained how cellulose treated with nitric acid in the presence of sulfuric acid was nitrated.  The cellulose molecule having three hydroxyl (—­OH) groups, can take up one, two or three nitrate groups (—­ONO_{2}).  The higher nitrates are known as guncotton and form the basis of modern dynamite and smokeless powder.  The lower nitrates, known as pyroxylin, are less explosive, although still very inflammable.  All these nitrates are, like the original cellulose, insoluble in water, but unlike the original cellulose, soluble in a mixture of ether and alcohol.  The solution is called collodion and is now in common use to spread a new skin over a wound.  The great war might be traced back to Nobel’s cut finger.  Alfred Nobel was a Swedish chemist—­and a pacifist.  One day while working in the laboratory he cut his finger, as chemists are apt to do, and, again as chemists are apt to do, he dissolved some guncotton in ether-alcohol and swabbed it on the wound.  At this point, however, his conduct diverges from the ordinary, for instead of standing idle, impatiently waving his hand in the air to dry the film as most people, including chemists, are apt to do, he put his mind on it and it occurred to him that this sticky stuff, slowly hardening to an elastic mass, might be just the thing he was hunting as an absorbent and solidifier of nitroglycerin.  So instead of throwing away the extra collodion that he had made he mixed it with nitroglycerin and found that it set to a jelly.  The “blasting gelatin” thus discovered proved to be so insensitive to shock that it could be safely transported or fired from a cannon.  This was the first of the high explosives that have been the chief factor in modern warfare.