Foreign Correspondence.-1. On the Science of the International Exhibition,-in a letter from O. C. Marsh, B. A.: Gold: Silver: Platinum and Platinum-metals, Aluminium: Mercury, Copper: New Metals: Iron and Steel: Coal and artesian boring: Canadian collections; asterism in Mica, 2. Correspondence of J. Nickles: Obituary: Henri Hurran de Senarmont, Adrian Etienne Pierre de Gasparin: Ed. Francois Jomard, Publication of the works of Lavoisier, Ozone and Nitrous Acid-Fixation of Nitrogen in Plants, Oxygen Gas to Counteract Gangrene: Treatment of Tubercular Leprosy, or the Red Disease of Cayenne, Preservation of Wood, The Ceramic Arts of the London Exhibition, Bibliography.- Recent publications by Hachette & Co., Paris, By H. Bossange, Paris, 3. Correspondence of T. Sterry Hunt, F.R.S.-On the nature of nitrogen and the theory of nitrification