MSS. intended for publication and books, etc., intended for review should be sent to the Editor of SCIENCE, Garrison-on-Hudson. N. Y. ''IIe~r~peI, ' Gas Analysis, " English translation b.y Dennis, 1906, p. 149. Z"Com~nercial oxygen as supplied in the trade has been qulte thoroughly investigated by the spcaker and Stevenson, loc. cit.