Letter from James Dewar, Royal Institution of Great Britain, London, to [Joseph] Larmor Apart from the experiment shown at the soiree and on 7 June, three Fellows have seen it in the laboratory: Lord Kelvin, [George] Liveing and Armstrong [William Crookes's name inserted] and they can give information. He gives an account of the experiment and questions arising from it; the radiometer does not record the emanation. [Ernest] Rutherford and [Frederick] Soddy showed no detectable electrometer effects below 150 degree centigrade. The radium and thorium are separated from the radiometer by means of charcoal cooled in liquid air or by liquid hydrogen. He thinks the effects must come from helium [?] or alpha particles, or from an unknown factor or a blunder. He gives a sketch of the experimental apparatus. He gives a second sketch, showing the apparatus in testing of the working pressure by means of the tension of mercury. 26 June 1907