John Tyndall, photographic portrait

JUL 19 1873

A dated photographic portrait of John Tyndall from 19 July 1873. Tyndall, working first with Knoblauch and later alone at the Royal Institution, spent the 1850s testing whether diamagnetism was a true polarity or a crystalline effect, and eventually collected the work as "Researches on Diamagnetism and Magne-Crystallic Action". A precisely dated period photograph.