Stellar Atmospheres, by Cecilia Payne

Cecilia Payne wrote her dissertation on the interpretation of stellar spectra. When it was published in 1925, it made quite a stir. Payne showed how one could extract the chemical composition of stars from their optical spectra, and came to the surprising conclusion that stars were largely hydrogen and helium.

Reproduced below is Chapter 8 of her dissertation, all in PDF format.