Here's the breakdown:

* Discovery in the Spectrum: Helium was first detected in 1868 by Pierre Janssen during a solar eclipse. He observed a bright yellow line in the spectrum of the sun's chromosphere, which was not attributed to any known element at the time.

* Discovery on Earth: It wasn't until 1895 that William Ramsay isolated helium on Earth. He discovered it as a gas emanating from a mineral called cleveite.

The difference between the spectral discovery and the terrestrial discovery was about 27 years, not 30.