and Departures in the United States. 127 



the ordinates of the black body at any one temperature. The 

 wave lengths of the bolometer curve above 1"0/^ seem to require 

 by their i>reatcr leugtli a solar temperature of about 7500° T, 

 while the wave len<>;ths of the curve from 000 /a to 1-00 ix 

 seem to be satisfied with somethino- like 6500° T. If the sun is 

 not radiatin"' as a pure black bod}^ as is very likely to be the 

 fact, it follows that the study of the solar energy of radiation 

 is an excessively complex problem. There is evidence from the 

 prominences that the sun has an excess of energy along one 

 diameter and a defect along the other at right angles to it ; 

 also, from the magnetic field that the areas of heat in solar 

 longitude, while very irregular like incipient oceans and conti- 

 nents, are yet capable of classification ; and, from the spectro- 

 scope that the great variations in the angular velocities at the 

 photosphere, as 26'7 days at the equator to 31"0 days at the 

 poles, or 26*0 near the level of the upper chromosphere over 

 the equator to 29*0 days at the poles. These point to great 

 changes in the local solar mass temperatures from ])lace to 

 place, though they may be deep seated. Such variations of the 

 heat of the radiation energy at the sun, and of the absorbing 

 and depleting capacities of the earth's atmosphere, render the 

 problem of direct radiation measures one of exceptional diffi- 

 ■cnlty. On the other hand, we have in the earth's magnetic 

 field one of the most sensitive, natui'al instruments for regis- 

 tering the effects of solar radiant energy, which will be 

 utilized before long in its highest functions. If ionization is a 

 direct product of radiation, and it is registered accurately 

 though indirectly in the magnetic field, it follows that this is 

 our easiest approach to a working method of handling the 

 materials in questions. It will doubtless require much more 

 labor to remove some of the barriers that still stand in our 

 way. The simple or superficial application of the standard 

 formulas of radiation to the temperature indicated in fig. 3, 

 will show how far we are from accounting for this distribution 

 by any of the elementary methods heretofore discussed. It 

 is necessary to separate the circulation effects from the radiation 

 effects, and to separate the incoming radiation effects from the 

 outgoing radiating effects. As none of these steps have yet 

 been taken, we may consider the subject of the relations 

 between radiation, temperature and circulation as virgin ground 

 for an extensive research. 



It is well to note the growth of interest and conviction in 

 the minds of students regarding the practical validity of this 

 solar-terrestrial problem. We have only to recall the numer- 

 ous papers on the subject in recent years, besides those of the 

 writer, by Langley, Abbot, Fowle, Lockyer, Clayton, Clough, 

 Artowski, Merecki, and the several International Commissions 

 on Solar Physics and Meteorology. 



U. S. Weather Bureau, Washinston, D. C. 



