REFERRING to Prof. B. N. Menschutkin's letter in NATURE of June 23, Dr. G. Rudorf, 46, Lanchester Road, Highgate, N.6, writes to point out that German translations of Mendeléeff's papers are readily available in Ostwald's “Klassiker” (No. 68). A German translation of Mendeléeff's second long paper also forms part of supplement vol. 8 (1871) of Liebigs Annalen. Mendeléeff published a third table in 1880 (Ber. Chem. Ges., vol. 13, p. 1766).