NATURE 



THURSDAY, SEPTEMBER 12, 191: 



THERMODYNAMICS OF THE 

 ATMOSPHERE. 

 Thennodynamik der Atmosphiire. By Dr. A. 

 \Vegener. Pp. viii + 331. (Leipzig:: J. A. 

 Bartli, 191 1.) Price 11 marks. 



THE progress of a science depends upon the 

 intellectual calibre of the men who pursue 

 it : that determines what shall be written for them 

 as well as by them. It is therefore significant for 

 meteorology that a text-book on the thermo- 

 dynamics of the atmosphere should be added to 

 a collection recently enriched by treatises on 

 meteorological optics and on the foundations of 

 dynamical meteorology- Special phases of the 

 subject have been treated at some length by 

 Helmholtz, Hertz, von Bezold, and others, but 

 their papers are scattered among different scientific 

 journals, rarely accessible in a single library. 

 Dr. Wegener's treatise, which has been written 

 with the object of giving a systematic account of 

 the existing knowledge and methods, should there- 

 fore be generally welcomed. 



In an introductory chapter the author deals with 



the constitution of the atmosphere, and discusses 



in interesting fashion the extreme heights at which 



ais optical phenomena, aurora, meteors, and 



liacal light appear. He finds that in all cases 

 ne values lie roughly between 70 and 100 km., or 

 ■n the layer in which the nitrogen atmosphere is 

 changing to the hydrogen atmosphere. After an 

 account of the thermodynamics of an ideal gas 

 and its application to a consideration of the precise 

 proportions in which different gases exist at dif- 

 ferent heights, he indulges in some speculation 

 about the existence of a hypothetical gas, geo- 

 coronium, above the hydrogen atmosphere. Such 

 speculation is out of place in a text-book, and the 

 same criticism applies to the statement that the 

 stratosphere extends from 11 to 70 km. There 

 is no evidence as to the upper limit of the tem- 

 perature conditions characteristic of the strato- 

 sphere. 



In the third section the different phases of 

 water vapour, the condensation on nuclei, and 

 the formation of crystals are discussed thoroughlv 

 and comprehensively. 



The fourth and fifth sections, which comprise 

 rather more than two-thirds of the book, are 

 undoubtedly the most valuable parts of the work. 

 In them the author treats of the thermodynamics 

 of adiabatic changes and of the physics of clouds 

 respectively. The effect of the condensation of 

 water vapour in diminishing the vertical tempera- 

 ture gradient for air rising adiabatically is impor- 

 NO. 2237, VOL. 90] 



tant both in the general circulation and in local 

 disturbances, and it is usually put forward as the 

 explanation of the Fohn. The cooling of the air 

 which rises on the windward side of the moun- 

 tains is influenced by the condensation and pre- 

 cipitation of the water which it contains. This air 

 descends on the lee side, where there is no 

 moderating effect on the vertical temperature 

 gradient, and is consecjuently hot and dry. Dr. 

 Wegener deduces, from the fact that the average 

 vertical gradient is less than that corresponding 

 to the adiabatic gradient either for saturated or 

 for dry air, that the rising of the air on the wind- 

 ward side actually exerts a moderating influence 

 on the Fohn. 



A very full account is given of "inversions," 

 i.e. cases in which the temperature remains con- 

 stant or increases with increasing altitude. Their 

 connection with waves and wave-clouds is dis- 

 cussed at length, and the form of the surface 

 between currents of different densities and veloci- 

 ties is made the subject of mathematical investiga- 

 tion. A chapter is devoted to the stratosphere. 

 The different types of the temperature-height curve 

 between the troposphere and stratosphere are illus- 

 trated by an excellent diagram derived by 

 Schmauss from a consideration of the results 

 obtained at Munich. In the discussion of the 

 meteorological conditions in the stratosphere itself 

 it is assumed that the relative humidity at the 

 base of the stratosphere, the region of minimum 

 temperature, is 50 per cent. As there is no process 

 by which the nitrogen-oxygen atmosphere is 

 " dried " except by the precipitation of water con- 

 densed by cooling, it is not easy to see how a 

 relative humidity of 50 per cent, could be obtained 

 at the place of minimum temperature, where dif- 

 fusion and convection would both tend to produce 

 saturation. 



The discussion of clouds is excellent. It in- 

 cludes a note on the rate of fall of drops and its 

 connection with the passage from cloud to rain. 

 The photographs of the different forms of clouds, 

 some of which were taken from balloons above 

 the clouds, are well reproduced, and add consider- 

 ably to the educational value of the descriptive 

 matter and the theoretical discussion. 



Dr. Wegener has performed a signal service in 

 producing a good book on a branch of the subject 

 which had not ■ previously been dealt with sys- 

 tematically. The work as a whole loses by the 

 deliberate exclusion of radiation, which is funda- 

 mentally and indissolubly connected with the 

 application of thermodynamic considerations to the 

 problems which confront the meteorologist every 

 day. The author regards it, however, as a subject 

 for separate treatment. 



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