In 1884, William Thomson, 1st Baron Kelvin, delivered twenty lectures on molecular dynamics and the wave theory of light. Kargon wrote (page 2):The sessions, which were held in a small lecture hall, were conducted as "master classes". The tone was conversational and informal; Kelvin made almost no use of notes ... Usually Kelvin lectured from one of these standpoints, then engaged the audience in a discussion of the details, then shifted to another of the standpoints for the second part of the lecture.