Letter from William Crookes, 7 Kensington Park Gardens, London, W., to [Alan Archibald Campbell] Swinton Esq., 66 Victoria [Street], S.W. Apologises for a delayed reply. Does not think any determinations of the melting point of rubies have been made but if there are any they must be less accurate than those Swinton is making, encouraging him to continue the work. Mentions that [John] Joly made some exact determinations of high temperatures many years ago but was limited by the fusing point of platinum. 7 January 1908