Hydrogen was discovered by the famous English physicist the Hon. Henry Cavendish. He was the richest of the learned and the most learned of the rich, as one of his contemporaries put it. We might add that he was the most punctilious of scientists. It is said that whenever Cavendish borrowed a book from his own library he always signed his name on the book card. The most sedate of scientists, devoted entirely to scientific research, always engrossed in his science, he got the reputation of an eccentric recluse. But it was just these qualities that enabled him to discover the new gas hydrogen. And, believe us, it was no easy task!

   He made his discovery in 1766, and by 1783 the French Professor Charles had flown the first hydrogen-filled balloon.

   Hydrogen was a most valuable find to chemists, too. It helped them to get an insight into the structure of acids and bases, these most important classes of chemical compounds. It became an indispensable laboratory reagent for precipitating metals from solutions of salts, and for reducing metallic oxides. And paradoxical though it seems, had hydrogen not been discovered in 1766, but, say, half a century later (such a thing could really have happened) the progress of chemistry, both in theory and practice, would have been retarded for a long time.

   When the chemists had come to know hydrogen well enough, and practical workers had begun to utilize it for the production of important substances, this gas drew the attention of physicists. And they found out a great deal of information which enriched science many times over.

   Do you need more evidence? For one thing, hydrogen solidifies at a lower temperature than any other liquid or gas (except helium), at minus 259.1° Celsius. Secondly, the hydrogen atom enabled the Danish physicist Niels Bohr to work out a theory of the arrangement of electrons around the atomic nucleus, without which the physical sense of the Periodic Law could not have been understood. And these facts laid the foundation for other very important discoveries.

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