PHYSICS OF THE GLOBE. 135 



These important volumes are worthy of much more ex- 

 tended notice, and ought to be in the hands of every stu- 

 dent of meteorology, and every observer as well. 



The "Vade Mecum" is divided into two parts: first, in- 

 struction to observers ; second, the meteorology of India. 

 The instructions are certainly clear, without superfluous 

 words, and every word to the point ; and, while especially 

 adapted to use in India, afford valuable suggestions for ob- 

 servers everywhere. The second part of " Vade Mecum " is 

 what especially interests the student of meteorology, as dis- 

 tinguished from the mere observer, and in the introduction 

 he states that in this part of his volume, a knowledge of the 

 laws that regulate the internal movements of the atmos- 

 phere is the business immediately before us. He entertains 

 the view, apparently very nearly correct, that in India we 

 have an epitome of atmospheric physics, even as in Eng- 

 land we have an epitome of strategraphic geology. 



The author gives the most recent results in his next 

 chapter on the physical properties of air and vapor. He 

 especially calls attention to the erroneous custom, now rap- 

 idly becoming obsolete, of subtracting the tension of aque- 

 ous vapor from the total barometric pressure. The diurnal 

 variation of vapor tension he partially explains as due to 

 the ratio between the rate of production and the rate of re- 

 moval. The effects of condensation of vapor in retarding 

 the fall of temperature are very fully developed. 



The conclusions of Tyndall in reference to the absorption 

 of heat by aqueous vapor are not adopted by him ; and he 

 inclines, with most physicists, to adopt the conclusions of 

 Magnus, confirmed, as they have been, by Hoorweg and Buff 

 namely, that air and vapor differ little in absorptive pow- 

 er; and that in atmospheric phenomena it is most important 

 to distinguish between true vapor and that which is in the 

 first stao-e of condensation. The results of direct observa- 

 tions on atmospheric absorption by Forbes, Hennessy, Hodg- 

 kinson, Xeumayer, Strachan, and Harrison are adopted by 

 Blanford to the general exclusion of purely physical theories. 



The dynamic heating and cooling of the atmosphere, as de- 

 duced from the dynamical theory of heat, are very fully ap- 

 preciated and exposed. The physical geography of India 

 has, as in every country, the greatest influence over its me- 



