46 .1. W. Greely — (jrcography of the Air. 



wind system of the earth, with the result of disseminating the 

 excess of temperature and humidity of tlie torrid zone over the 

 temperate and arctic zones, thereby producing the prevaiHng 

 winds. 



8. This is accompUshed by the prothiction of alternating local 

 depressions and elevations of barometric pressure by the dis- 

 turbance of indifferent equilibrium in the upper layers of the air. 



9. " Highs " and " lows " are a consequence of the tempera- 

 tures and velocities of the upper currents. 



Whence it follows that the most important problem of meteor- 

 ology is the investigation of the causes and consequences of the 

 disturbance of indifferent equilibrium of the atmosphere, and 

 the weightiest problem in weather prediction is the investigation 

 of the geographical origin or extraction of air currents pursuing 

 their course above us toward the pole. 



In Pomortsew's treatise on synoptic meteorology, published in 

 Russia, there are full chapters on prediction of Aveather, whether 

 from synoptic charts, from observations at a single place, or 

 from prognostics of great length based on researches on the suc- 

 cession of warm and cold months. It also contains Pomortsew's 

 investigations on the types of pressure distribution in eastern 

 Europe, as well as the average path of cyclones. 



The favorable opportunities afforded by the Eiffel tower have 

 been utilized by French meteorologists. M. Angot states that 

 during the anti-cyclone of November, 1889, the temperature on 

 the tower was several degrees higher than below. The change 

 of weather set in earlier, with a strong and warm wind, on the 

 tower, while the air at the ground was cold and calm. Wind 

 observations on tlie tower show a ratio of 3.1 at that height (308 

 meters) to the velocity at a height of 21 meters, as determined 

 from 101 days' observations, which, remarkable at such a small 

 height, discloses the peculiarity of high mountain stations. 



Partsch, writing on evidence of climatic changes within his- 

 torical times in the Mediterranean region, remarks that too much 

 attention has been given to changes in crops, the introduction of 

 plants, and the limits of domestic animals. He states that ex- 

 isting information as to the harvest time of ancient days indi- 

 cates an unchanged climate, while the land-locked lakes in Tunis, 

 which afford the best evidence on rainfall variation, show abso- 

 lutely no climatic change. 



