DYNAMIC METEOROLOGY. 371 



air Ferrel gives especial attention to the eflect of wave length upon the 

 law of diminution in a complex bundle of rays, sucli as those from the 

 sun, and shows that his formula and constants hold good for the visual, 

 the thermal, and the chemical elfects of the solar rays. (A special mem- 

 oir by him on radiation is published in the American Journal of Science, 

 Julyi 1889.) 



In chapter 2, on temperature of the atmosphere, Ferrel gives an ex 

 pression for the mean diurnal intensity of the snn's radiation developed 

 into a series as a function of the snn's declination and the observer's 

 latitude, which expression he also farther converts into a series de. 

 pending on the time and the observer's latitude. With this he then 

 combines the effect of the absorption by the earth's atmosphere, and 

 proceeds to discuss the conditions that determine the temperature at 

 any place and any time for a body of any shape and coefficient of ab- 

 sorption and radiation. The importantresults obtained in this chapter 

 depend principally upon the radiation observations of Prevostaye and 

 Desaius, Melloui, Langley, Duloug, and Petit, and are applicable to the 

 temperature of bodies at the earth's surface, the temperature shown by 

 thermometers and those shown by solar radiation apparatus. Especial 

 attention is given to the nocturnal cooling by radiation. (The late pub- 

 lications by Maurer, H. F. Weber, Angot and Zenker could of course 

 not be utilized by Ferrel.) 



In chapter 3 Ferrel deduces the general motions and pressure of the 

 atmosphere, beginning with the equations of absolute motion on the 

 earth at rest, whence follows his law that all bodies in motion are de- 

 flected to the right in the northern hemis[»here. Combining these equa- 

 tions with ihe equation of continuity, certain general relations are de- 

 duced expressed by differential eqnations. 



Ferrel's method of solution of these equations consists in successive 

 approximations, beginning with the simplest cases of no friction and no 

 distnrbance of the normal distribution of temperature, he finally pro- 

 ceeds in section 4 of chapter 3 to give a sjiecial solution for the actual 

 case of the earth, which although only approximate yet within the limits 

 indicated, appears to agree well with observed ])heuomena; this solu- 

 tion is summed up in the two following formuhe for the connection be- 

 tween the barometric gradient ((ir) expressed in millimeters per degree 

 of the great circle of the meridian from north to south, the angular dis- 

 tance (^) from the north pole or 90 degrees minus the latitude; the veloc- 

 ity [v) of the east-west motions of a particle of air ; the total velocity (-s) 

 of the particle; the temperature (r) on which the density of the air de- 

 I)euds ; the inclination {i) of the wind to the parallel of latitude ; the 

 observed barometiic pressure (P) and the normal sea level barometric 

 pressure (Po). The resulting formula for the barometric gradient meas- 

 ured on the meridian, as given on page 207 of his " Pecent Advances," is 



0.1571 t; cos ^ P 0.ir)7l .s cos $ P 



G= 



Cos^ j(l+0.U04 r) Po (1+0.004 7) cost P^ 



