TO the last issue of Science et Nature M. L. Mangin contributes an interesting account of the chemical laboratory recently installed on the Pic du Midi, Pyrenees, at an altitude of nearly 9500 feet above the sea. As shown in our first illustration, the laboratory stands between the dwelling-house and the Observatory, of which it forms a dependency, under the direction of MM. Müntz and Aubin. In the second illustration a fuller view is given of the building, which faces southwards, and the slated roof of which is so constructed as to constitute a sort of pluviometer registering the annual rainfall, and retaining sufficient for chemical analysis. This unique establishment, which promises to render great services both to meteorology and to the economic industries, is at present chiefly occupied with the constituent elements of the terrestrial atmosphere, especially in connection with vegetable life. The student of chemistry need scarcely be reminded that, besides oxygen and nitrogen, the air contains in smaller proportions carbonic acid, ammonia, and certain nitric compounds playing an important part in the nutrition of plants, and supplying them with nearly all the nitrogen and carbon that enter into the composition of their tissues. During the summer months of the years 1881-82, MM. Müntz and Aubin were mainly engaged with the quantitative analysis of these substances, under conditions peculiarly favourable for the prosecution of such investigations The results so far obtained may here be briefly resumed.