PRESENT PROBLEMS OF METEOROLOGY 745 



great whirls, the air which rises above the tropics flowing over 

 the trades and descending probably in the extra-tropical regions, 

 while around each pole is an independent cyclonic circulation. 1 

 Although this general circulation of the atmosphere appears to be 

 indicated, many details require to be investigated. In particular, 

 the movements of the masses of air overlying the trade-winds and 

 doldrums, which is a region nearly barren of upper clouds, are still 

 unknown, and the determination of these movements, as well as the 

 temperature and humidity of the different strata, by means of kites 

 flown from steamships, was suggested by the writer, since it would 

 be possible in this way to penetrate even the masses of quiescent 

 air which probably separate the trade-winds from the superposed 

 anti-trades. 2 This suggestion has already been put in practice on the 

 yacht of the Prince of Monaco in the neighborhood of the Azores, 3 

 but a more extensive campaign is necessary, which the writer him- 

 self hopes to undertake, if the funds necessary to charter and equip 

 a steamer can be procured. 



Here it will be encouraging to state some results of the efforts to 

 ascertain the vertical thermal and hygrometric gradients in the 

 atmospheric ocean, and to show what may be accomplished in the 

 future. Observations on mountains, as we have seen, cannot be 

 expected to give the conditions which exist at the corresponding 

 heights in the free air, and hence the necessity of sending observers 

 or self-recording instruments into this medium through the agency 

 of balloons and kites. By the aid of an international commission, 

 formed eight years ago under the direction of Professor Hergesell 

 at Strassburg, much has been accomplished in Europe in this way, 

 and something in this country through kite-flights. At the present 

 time such atmospheric soundings are made once a month in most 

 European countries, and at Blue Hill in the United States, with the 

 result that a knowledge is being acquired of the vertical gradients 

 of the meteorological elements which entirely contradicts previous 

 conceptions. For example, it was formerly supposed that the tem- 

 perature diminished with increasing altitude more and more slowly, 

 and that at a height of about ten miles it remained invariable during 

 winter and summer and above pole and equator. But the recent 

 investigations of my colleagues in France and Germany show that 

 the temperature decreases faster and faster as one rises in the air, 

 and that not only is there a large seasonal variation at the greatest 

 heights attained, but that non-periodic changes occur from day to 

 day, as they do at the earth's surface.* Still more remarkable is the 



1 Quarterly Journal of Royal Meteorological Society, vol. xxx, pp. 322-343. 



2 Monthly Weather Review oi United States Weather Bureau, vol. xxx, pp. 181- 

 183. 



3 Nature, vol. LXXI, p. 467. 



* Monthly Weather Review, vol. xxx, pp. 357-359. 



