Letter from J [Joseph] Larmor, St John's College, Cambridge, to Mr King [? possibly Louis Vessot King] Larmor believes there is a discrepency in his correspondent's discussion of pressure and Zeeman effects. He has looked up the note referred to, giving details, and saying that this makes changes in wavelength to be proportional to the wavelength, comparing this to the Zeeman effects proportional to its square. Unless Larmor is mixed up, the two effects are in the same direction but opposite. His pressure shifts show no sign of any definite relation to wavelength. Larmor discusses this with equations, concluding that 'the matter is not amenable very well to test'. 9 July 1910