Yeah, blunder. Wikipedia says:

In the 1820s both John Herschel and William H. F. Talbot made systematic observations of salts using flame spectroscopy. In 1835, Charles Wheatstone reported that different metals could be easily distinguished by the different bright lines in the emission spectra of their sparks, thereby introducing an alternative mechanism to flame spectroscopy.

It wasn't until the 1850s that Ångström discovered that elements both emit and absorb light at characteristic wavelengths, which is what spectroscopic analysis of stars is based on, so I'm leaning toward justifiable.

On the subject of stars, all investigations which are not ultimately reducible to simple visual observations are…necessarily denied to us… We shall never be able by any means to study their chemical composition.

Well, the first half seems approximately correct. The second sentence should have begun with "And by clever application of this means we shall...".