106 



DISPLACEMENT INTERFEROMETRY APPLIED TO 



ferences. There are other details to be left for solution to the future, which 

 remain obscure. The ball M acts more effectively than the pier because the 

 former is nearer the mass m. Nevertheless one is at liberty to preserve an open 

 mind in suspecting that, associated with the thermal radiation, some other 

 form of radiation may be entering. These surmises, however vague, will be 

 again suggested by much of the work below, with apparatus //. 



Curves for daily changes of temperature A0, sunshine, etc., were also tested, 

 but with no agreement superior to the above. This is the particularly puzzling 

 feature ; for it seems as if the absolute atmospheric temperatures and not their 

 daily variations were effective ; for otherwise there is no more reason why the 

 Ay should not approach a given mean value at low temperatures as well as 

 high temperatures. In the July observations so far as taken, however, Ay 

 is low at low atmospheric temperatures and high at high temperatures. 



The results for August, in figure 121, follow in their a. m. and p. m. values 

 only, as this makes for greater clearness. The two curves differ as to details, 

 remembering that the a. m. curves are subject to the sunlight which strikes the 

 outside of the east wall. They are larger as a rule and the curves cross but 

 rarely. Each a. m. excursion reappears in subdued form in the p. m. results. 



If we again make the comparison with atmospheric temperature, conclusions 

 similar to those already made may be drawn. Thus, the region c is char- 

 acterized by two maxima, the region d by two minima, and the indentations of 

 the high region c may be followed until they are modified by the copious warm 

 rain. Finally, as the temperature data are means for 24 hours, while the values 

 of Ay are obtained from observations between 10 a. m. and 6 p. m., complete 

 correspondence would be impossible. 



In August, however, considerably greater correspondence with the curve of 

 daily temperature changes (Ad) may be detected. Though there is no im- 



