238 proceedings: Washington academy 



and irregular fluctuations in the intensity of its thermal radiations, or 

 to some of these variously in combination, etc. 



"Even suppose these solar phenomena directly influence terrestrial 

 weather in some way yet to be proved, is it not plainly most essential 

 in detecting and analyzing cause and effect relations that we adequately 

 segregate and make due allowance for the complex phenomena which 

 clearly must result if solar insolation were perfectly constant and if 

 the other manifestations of solar activity were entirely absent? 



"Those who have been most ready to find convincing evidence of 

 definite relations between terrestrial weather and minor features of 

 solar activity have seemingly disregarded the obligation devolving 

 upon them to make the segregation between the major and the minor 

 influences. . . 



"Variations in the intensity of thermal radiations from the sun must, 

 of course, be reflected in terrestrial weather phenomena, but such 

 reflected eft'ects must stand in appropriate relation quantitatively to 

 the variations themselves." 



These considerations prevent me from concurring in Mr. Clayton's 

 conclusions which he states in his own words as follows: 



"The results of these researches have led me to believe: i. That if 

 there were no variation in solar radiation the atmospheric motions 

 would establish a stable system with exchanges of air between equator 

 and pole and between ocean and land, in which the only variation 

 would be daily and annual changes set in operation by the relative 

 motions of the earth and sun. 2. The existing abnormal changes, 

 which we call weather, have their origin chiefly, if not entirely, in the 

 variation of solar radiation." 



Mr. Clayton's paper in no way defines what constitutes a "stable 

 system" of atmospheric motions nor does it offer a direct proof of these 

 conclusions. They are simply generalized inferences drawn by him 

 from his investigations. 



I realize that my own statement as well as that of Mr. Clayton is 

 of a kind that it is difficult or impossible to prove or disprove. They 

 are contradictory, however, and I leave them to your reflection as to 

 their physical soundness. 



(2) I am most reluctant to raise any question as to the final accuracy 

 of Dr. Abbot's solar radiation values, because I know the conscientious 

 care he has taken to eliminate systematic errors due to terrestrial 

 causes. However, this is a matter about which we must have a definite 

 answer, yes or no. Dr. Abbot fully recognizes the importance of this 

 issue, and, in his introductory note to Clayton's paper, he states the 

 question in this way: 



"I now anticipate the question of the reader: .... is it pos- 

 sible that the apparent variations of radiation were not truly solar, 

 but were caused by changes in the transmissibility or other properties 

 of the air which affected the solar radiation measurements in one way 

 and the temperature and rainfall of the earth in another?" 



