Copy letter from Francis Alexander Towle, Assistant Secretary of the Royal Society; to the Director of the National Physical Laboratory Informs the Director that the Royal Society would be pleased to have the following exhibits offered for the May Soiree: 1. Flutter of model aeroplane wings by Mr Frazer and Mr Duncan 2. Measuring thickness of films by Mr Rolt and Mr Barell 3. (a) Manganese and (b) Age-hardening of aluminium alloys by Dr Gayler and Mr Preston. 17 April 1929