Rendiconti del Reale Istituto Lombardo, June 16.—On the importance of the qualitative bacteriological examination of potable waters, by Prof. Leopoldo Maggi. Attention is directed to the mistake made by many chemists, who occupy themselves exclusively with the quantitative examination of potable waters, neglecting the much more important question of the specific quality of the germs, owing to the greater difficulty of distinguishing between the various forms of these organisms. Waters largely charged with harmless Bacteria are condemned, although perfectly drinkable, while others apparently pure, but really containing deadly germs in small quantity, are declared to be quite safe, often to the great clanger of the public health. It is in fact far more a question of qualify than of quantity, as shown especially by the recent researches of Chantemesse and Vidal on the Bacillus of typhus. On the other hand, Leone has experimentally shown that comparatively pure water is itself a medium of culture, so that a small quantity of innocuous Bacteria may largely increase in it without rendering its use dangerous. Some instructions are added for distinguishing between harmless organisms normally present in water as their natural element, and pathological germs, which render it quite unfit for human consumption.—Meteorological observations made at the Brera Observatory, Milan, during the month of May.