Rayleigh (John William Strutt, 3rd Baron) Autograph letter signed ('Rayleigh') to Henry Currie Marillier, apologising for not responding to a request from a journalist, and adding 'I am now getting to work at the Roy[al] Inst[itution], I shall be setting up duplicates of my counting [?] apparatus for separation of argon. In a week or two I hope this will be at work & I s[houl]d be happy to show it to you', three pages, 8vo, Carlton Gardens, London, 6 February 1895. ***Rare letter by Rayleigh on the discovery of argon, written only a week after its announcement at a meeting of the Royal Society on 31 January 1895. The discovery was to bring Nobel prizes in 1904 for Rayleigh and William Ramsay.