778 



SCIENCE 



[N. S. Vol. XXXII. No. 831 



the growing interest in the subject is at- 

 tested in nearly every mail by the arrival 

 of important and valuable papers in these 

 subjects. The ionization of the atmos- 

 phere and its consequences in a circu- 

 lating medium form an inexhaustible field 

 for valuable investigations. 



The General Circulation of the Atmos- 

 phere. — These observations have been the 

 means of subjecting to critical examina- 

 tion the theoretical researches of Farrel 

 and of Oberbeck on the general circulation 

 with the result that they are distinctly de- 

 fective. This circulation is not so simple 

 as was assumed in the elementary canal 

 theory upon which their integrations were 

 based, and, unfortunately, the actual cir- 

 culation is too complex to admit of any 

 simple hydrodynamic treatment. The canal 

 theory assumes a simple overflow from the 

 equator to the poles in the upper levels, 

 with return iinderflow towards the equator 

 in the lower levels. Our cloud work first 

 proved that there is an interflow in all 

 levels from the ground upwards, being a 

 maximum in the 2-mile level, by which 

 warm currents from the south interpene- 

 trate cold currents from the north, and 

 under the force of gravity set up a mixing 

 circulation which produces cyclones and 

 anticyclones. These southerly warm cur- 

 rents in the lower levels were called 

 "leakage" currents, and their function 

 was to break up the high pressure belt 

 into large centers of action, around which 

 the interchange of heat goes on rather than 

 above and below an assumed neutral plane 

 of motion. 



At the same time the source of the heat 

 energy that drives cyclonic storms, hurri- 

 canes and tornadoes was shifted from the 

 latent heat of condensing water vapor, as 

 assumed by Espy and advocated by Farrel 

 and Abbe, to the heated masses of air 

 whose temperature has been raised pri- 



marily in the tropics by solar radiation. 

 Masses of air of difi:erent temperatures 

 have their pressure-levels shifted in such a 

 way that the force of gravitation tends to 

 produce nearly horizontal currents, which 

 sustain the mechanical interflow of cold 

 and warm masses in a mixing circulation 

 that gradually tears them to pieces, and re- 

 duces the disturbed temperatures to the nor- 

 mal values of their locality. My study of the 

 distribution of temperatures between the 

 equator and the poles in all latitudes, be- 

 tween the surface and 16,000 meters in ele- 

 vation, has resulted in a very diiSerent pic- 

 ture from that heretofore presented. It has 

 been assixmed that the maximum tempera- 

 tures in the levels 1,000-10,000 meters is 

 over the equator, but I find that it is lati- 

 tudes -j- 33° and — 33° approximately, in 

 the high pressi^re belt, and that there is a 

 distinct depression of temperature over 

 the tropics, with a maximum at the 2-mile 

 level. This is the only distribution of heat 

 in harmony with the known velocities in 

 the general circulation. Thus, the depres- 

 sion of temperature in the tropics is due 

 to vertical adiabatic circulation, and the 

 maximum in the high pressure belt is due 

 to the downward settling of air from the 

 higher levels, so that the real canal circu- 

 lation is chiefly confined to latitudes within 

 50 degrees of the equator. The mechanical 

 equations of motion require an increase in 

 temperature from the equator towards the 

 high pressure belt, in order to produce the 

 westward drift and trade winds, of the 

 tropics; there must be a decrease of tem- 

 perature from this maximum towards the 

 poles to produce the eastward drift in the 

 temperate and polar zones. The velocity 

 of circulation is proportional to this change 

 of temperature gradient on a given level, 

 and hence there is maximum westward 

 component in the 2-mile level over the 

 tropics, especially near the high pressure 



