TEE METEOROLOGY OF THE FUTURE 31 



of other air on each side of it, and it is quite possible that the flow of 

 the southwest monsoon, at any place and time, may be affected by some- 

 thing that occurred long before in a very distant part of the globe. At 

 first it was thought that the condition of the snow lying on the ground 

 in the Himalaya Mountains would determine the movement of the 

 monsoon and the amount of rain in the lowlands, but, as I have else- 

 where stated, the supply of air to the southern Indian Ocean must ulti- 

 mately come from the great westerly winds of the roaring forties, and 

 therefore the Asiatic circulation must be affected by the condition of 

 affairs in south Africa and the south Pacific and even the south Atlantic 

 oceans. 



On November 14, 1896, simultaneous balloon ascensions were made 

 from St. Petersburg and Munich and from intermediate cities, in the 

 midst of an area of high pressure that was moving slowly eastward over 

 Europe.' My study of these observations in the light of my maps of 

 high-level isobars for the northern hemisphere* gave occasion for the 

 following long range forecast which was made early in December,^ and, 

 of course, long before we received any reports from India, " As a result 

 it is quite possible that this area may have brought to upper India 

 light snow followed by cold dry weather about the first of December, 

 1896." 



As this prediction was abundantly verified, as shown by the reports 

 which we received a year later, it may be worth saying that the study of 

 these upper isobars explains why the areas of high pressure over North 

 America usually move at first from the northwest; subsequently their 

 velocity diminishes while the path turns more nearly eastward ; on the 

 other hand, similar areas of high pressure and cold air in Europe are 

 apt to come from the northeast before they turn southeastward. 



It seems certain that the atmosphere is so mobile that whatever 

 happens on one side of the globe will soon be known by its results on the 

 opposite side. Whatever happens in the atmosphere fifteen miles above 

 the earth will soon produce results at the earth's surface far away. 

 Meteorology must embrace the whole atmosphere above and below, north 

 and south, east and west. 



I suppose that the most important problem of the present time is to 

 attain a clear idea of the mechanics of the earth's atmosphere as a whole. 

 We separate this problem into three closely related divisions. First we 

 treat the atmosphere as we would a liquid of very rare but uniform den- 

 sity. Next we introduce the idea of a gas which enlarges or contracts in 

 volvmie with every change of pressure or temperature. 



Finally we pass from simple dry air and moisture to study the 



•See Monthly Weather Review, November, 1896, p. 415. 



* Published as chart VII. in that number of the Review. 



* See p. 420 of that same number of the Review. 



