High Climber

Jules Janssen spent a lot of time in high places. The French astronomer viewed a solar eclipse from the Himalayas. He escaped from Paris in a hot air balloon. And he almost died while in the mountains of South America.
But 125 years ago this week, he topped even those feats. He took the first observations from a small observatory at the summit of Mont Blanc, the tallest mountain in Europe — almost 16,000 feet high.
Janssen specialized in studying the Sun. And one problem intrigued him. He wasn’t sure whether oxygen in the Sun’s spectrum came from the Sun itself, or from Earth’s atmosphere. He’d taken spectra from different altitudes, but wanted to go higher. So he picked Mont Blanc.
Building an observatory there took a major effort. The summit was covered with ice, so there was no rock to anchor the observatory. And everything had to be carried to the top by hand.
The observatory was finished in September of 1893. Janssen, who was nearing 70, was carried up the mountain in a sled on th