3. Its Chemical Composition.-Oxygen and Nitrogen.-Carbonic Acid.- Sources of Vitiation and of Renovation.-Aqueous Vapour.-Accidental 31. Differential Barometers.-The Mercurial Gauge.-The Spring Pressure 32. The Anemometer.-Lind's Anemoscope.-Osler's Anemometer 35. Relations subsisting between the Density, Elasticity, and Temperature of |