Mark Twain said that he could understand something about how astronomers could measure the distance of the planets, calculate their weights and so forth, but he never could see how they could find out their names even with the largest telescopes. This is a joke in astronomy but it is not in chemistry. For when the chemist finds out the structure of a compound he gives it a name which means that. The stuff came to be called "caoutchouc," because that was the way the Spaniards of Columbus's time caught the Indian word "cahuchu." When Dr. Priestley called it "India rubber" he told merely where it came from and what it was good for. But when Harries named it "1-5-dimethyl-cyclo-octadien-1-5" any chemist could draw a picture of it and give a guess as to how it could be made. Even a person without any knowledge of chemistry can get the main point of it by merely looking at this diagram: C C C---C || || || | C--C C C--C C | | --> | | C C--C C C--C || || | || C C C---C [Illustration: isoprene _turns into_ caoutchouc] I have dropped the 16 H's or hydrogen atoms of the formula for simplicity's sake. They simply hook on wherever they can. You will see that the isoprene consists of a chain of four carbon atoms (represented by the C's) with an extra carbon on the side. In the transformation of this colorless liquid into soft rubber two of the double linkages break and so permit the two chains of 4 C's to unite to form one ring of eight. If you have ever played ring-around-a-rosy you will get the idea. In Chapter IV I explained that the anilin dyes are built up upon the benzene ring of six carbon atoms. The rubber ring consists of eight at least and probably more. Any substance containing that peculiar carbon chain with two double links C=C-C=C can double up--polymerize, the chemist calls it--into a rubber-like substance. So we may have many kinds of rubber, some of which may prove to be more useful than that which happens to be found in nature. With the structural formula of Harries as a clue chemists all over the world plunged into the problem with renewed hope. The famous Bayer dye works at Elberfeld took it up and there in August, 1909, Dr. Fritz Hofmann worked out a process for the converting of pure isoprene into rubber by heat. Then in 1910 Harries happened upon the same sodium reaction as Matthews, but when he came to get it patented he found that the Englishman had beaten him to the patent office by a few weeks.