. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. 402 RECORD OF SCIENCE FOR 1887 AND 1888. Moreover, the curves of condition are in winter nearer the plane jjoi; than in summer, because in winter the absolute quantity of aqueous vapor contained in the air is always smaller. When the air rises in the cyclone, starting from the initial condition a, the indicator-point very nearly follows the adiabatic until it attains the upper limit of the mass of clouds; in fact, below this limit the insol
. Annual report of the Board of Regents of the Smithsonian Institution. Smithsonian Institution; Smithsonian Institution. Archives; Discoveries in science. 402 RECORD OF SCIENCE FOR 1887 AND 1888. Moreover, the curves of condition are in winter nearer the plane jjoi; than in summer, because in winter the absolute quantity of aqueous vapor contained in the air is always smaller. When the air rises in the cyclone, starting from the initial condition a, the indicator-point very nearly follows the adiabatic until it attains the upper limit of the mass of clouds; in fact, below this limit the insolation and the radiation can produce only inappreciable effects. As for the rest, in so far as the curve departs from the adiabatic, it approaches the axes, contrary to what happens in the summer time. In the accompanying diagram, Fig. j.^ 7, abe is the curve of conditions from I the initial point a up to the moment \ when the comjjression begins. We have supposed that the initial ruass passes immediately from the dry stage ab to the snow stage be. It is probable that at high altitudes the compression of the descending air Ta proceeds adiabatically, according to the adiabatic of the dry stage; but V nearer the ground the radiation causes Fig. 7.—Adiabatics. i • , • , •, ,-, t , a deviation toward the co-ordinate axis ov. Thus one obtains a curve somewhat analogous to cd in Fig. 7. The curve cd is only a graphic representation of the well-known fact that there is an inversion in the vertical distribution of tempera- ture during clear days in winter. Near d the curve apjjroaches the line of saturation, so that it may even intersect it; this case corresponds to the formation of fog at the surface of the ground. Numerical data are wanting to determine whether the passage from c to ^ can be made in any other manner, as when the cooling exerts its action near the point c. The curve of condition in the plane jwi' would then possess a double point. These examples suffice to enab
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