In studying the total solar eclipse of 1868 the English astronomer Lockyer and the French astronomer Janssen passed the blinding light of the solar corona through a spectroscope prism. In the dense palisade of spectral lines they observed some that could belong to none of the elements known on Earth. Thus was discovered helium, the name coming from the Greek for "solar." Only twenty-seven years later did the English physicist and chemist William Crookes discover helium on Earth.

   His discovery proved contagious. Astronomers began to point their telescopes at distant stars and nebulae. Their findings were scrupulously published in astronomical yearbooks, and some even found their way into chemical journals. These were findings which treated of alleged discoveries of new elements in the boundless space of the universe. The elements were given pompous names such as coronium and nebulium, archonium and protofluorine. Apart from their names, chemists knew nothing about them. But bearing in mind the happy end of the helium story, they hurried to place these celestial strangers in the Periodic System. They put them before hydrogen or in the space between hydrogen and helium. And they cherished the hope that at some time in the future new Crookeses would prove coronium and its no less mysterious fellows to exist on Earth.

   But as soon as the physicists tackled the Periodic System these hopes were shattered. Atomic weights were found to be an unreliable footing for the Periodic Law. They were replaced in this function by the nuclear charge, or the atomic number of the element. In passing from element to element in the Periodic System this charge increases by one unit each time.

   Time passed and more precise astronomic instruments scattered the myth of the mysterious nebulae. They turned out to be atoms of long known elements, atoms that had lost some of their electrons and therefore gave unfamiliar spectra. The "business cards" of the celestial strangers proved false.

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