744 COSMICAL PHYSICS 



The mathematical application of the theory of a rotating sphere 

 surrounded by a heated atmosphere to explain the circulation of the 

 atmosphere as we find it, has not been satisfactory, owing to our lack 

 of knowledge of the conditions of the upper air, as well as our ignor- 

 ance concerning the physical properties of the atmosphere itself. To 

 acquire the latter knowledge, research laboratories must be estab- 

 lished at selected points, at both high and low levels, and as subjects 

 of study there may be mentioned the determination of the amount of 

 heat received from the sun and its secular variation, if any, the radiat- 

 ing and absorbing power of the air, the relation of pressure, density, 

 and temperature, the chemical composition of the air, its ionization 

 and radioactivity, and other investigations which have been proposed 

 by Professors Abbe and McAdie 1 in their pleas for the creation of such 

 aerophysical laboratories. The observatory now under construction 

 by the United States Weather Bureau on a mountain in Virginia will, 

 it is hoped, enable some of these problems to receive the attention 

 which they deserve. 2 



The average circulation of the lower atmosphere is now well known, 

 by reason of the monumental work of Lieutenant Maury on the winds 

 over the oceans, and from the mass of data since collected over 

 oceans and continents through the meteorological organizations 

 of the various countries. While, naturally, much less is known re- 

 garding the circulation of the upper air, a great deal has been ascer- 

 tained from the observations of clouds that were instituted a few 

 years ago in various parts of the world by an international commission. 

 In order to insure that the same cloud should everywhere be called 

 by the same name, it was necessary to instruct the observers by 

 publishing a cloud-atlas, 3 containing pictures and descriptions of 

 the typical forms of clouds which experience has shown to be iden- 

 tical all over the globe. Then, during one year which had been agreed 

 upon, measurements of the direction of drift and the apparent 

 velocity of the several cloud-types were made at many stations, 

 and measurements, by trigonometrical or other methods, of the 

 height of these clouds above a few selected stations enabled the 

 true velocity of the air-currents to be determined up to the altitude 

 at which the cirrus clouds float. 4 Thus an actual survey of the 

 direction and speed of the atmospheric circulation at different levels 

 was effected, and a recent discussion of the results by Professor 

 Hildebrandsson shows that the theories which have been held 

 heretofore are untenable. Professor Hildebrandsson's conclusions in 

 brief are that there is no exchange of air between poles and equator, 

 the circulation over the oceans, at least, resolving itself into four 



1 Smithsonian Miscellaneous Collections, vol. xxxix, no. 1077. 



2 National Geographic Magazine, vol. xv, pp. 442445. 



3 Atlas International des Nuages, Paris, 1896. 



4 Quarterly Journal of Royal Meteorological Society, vol. xxx, pp. 317-322. 



