This spectroscope is similar if not the same as used by Professor Crookes when he discovered thallium in 1861.

I wonder what Professor Crookes would have been able to discover if he had the Vreeland Spectroscope/spectrograph (http://www.silverprospector.com/assaying/vreeland.html)

Additional web-pages for earlier and later spectroscopes
http://www.chemteam.info/Chem-History/Kirchhoff-Bunsen-1860.html
http://www.superstock.com/stock-photography/Spectra
http://www.sciencemuseum.org.uk/broughttolife/objects/display.aspx?id=4651
http://www1.sciencemuseum.org.uk/hommedia.ashx?id=7321&size=Large